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Title:
PHOSPHORAMIDATE ANALOGS OF 5-FLUORO-2'-DEOXYURIDINE
Document Type and Number:
WIPO Patent Application WO/1993/006120
Kind Code:
A1
Abstract:
The present invention provides a series of cytotoxic phosphoramidate analogs of 5-fluoro-2'-deoxyrudine of general formula (I), wherein R1 is H, F or (C1-C4)alkyl; R2 is CH2CH2X wherein X is Cl, Br, I or p-toluenesulfonyl; R3 is (C1-C4)alkyl or CH2CH2X wherein X is Cl, Br, I or p-toluenesulfonyl; or wherein R2 and R3, taken together with the N atom, can be 5- or 6-membered heterocyclic ring which is aliphatic or aliphatic interrupted by a ring oxygen or a second ring nitrogen; R4 is H, one equivalent of a pharmaceutically-acceptable cation or (4,4,6-trimethyltetrahydro-1,3-oxazin-2-yl)ethyl, and the pharmaceutically acceptable salts thereof.

Inventors:
Borch, Richard F.
Fries, Kristin M.
Application Number:
PCT/US1992/007792
Publication Date:
April 01, 1993
Filing Date:
September 15, 1992
Export Citation:
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Assignee:
UNIVERSITY OF ROCHESTER.
International Classes:
A61K31/70; A61K31/7042; A61K31/7052; A61K31/7064; A61K31/7072; A61P35/00; C07H19/10; (IPC1-7): A61K31/70; C07H19/10
Domestic Patent References:
WO1989009221A11989-10-05
Foreign References:
EP0331032A11989-09-06
Other References:
JOURNAL OF MEDICINAL CHEMISTRY vol. 23, no. 6, June 1980, WASHINGTON US pages 661 - 5 J.S.PARK ET AL. 'Oxime amd Dithiolane Derivatives of 5-Formyl-2'-Deoxyuridine and their 5'-Phosphates: Antiviral Effects and Thymidylate Synthetase Inhibition.'
CHEMICAL ABSTRACTS, vol. 98, no. 1, 3 January 1983, Columbus, Ohio, US; abstract no. 4751s, 'Pharmacologically Active 5-Fluorouracil Derivatives.' page 428 ;column 2 ;
Download PDF:
Claims:
HAT IS CLAIMED IS:
1. A compound of the formula: wherein R1 is H, F or (CiCA)alkyl; R2 is CH2CH2X wherei X is Cl, Br, I or p_toluenesulfonyl; R3 is (C!CA)alkyl or CH2CH2X wherein X is Cl, Br, I or p_toluenesulfonyl or wherein R2 and R3 taken together with the N atom are a 5 or 6membered heterocyclic ring which is ali phatic or aliphatic interrupted by a ring oxygen or a second ring nitrogen; R4 is H, one equivalent of a pharmaceuticallyacceptable cation or (4,4,6trimethy tetrahydrol,3oxazin2yl)ethyl, and the pharmaceuti cally acceptable salts thereof.
2. The compound of claim 1 wherein R1 is F.
3. The compound of claim 1 wherein R1 is CH3 or H.
4. The compound of claim 1 wherein R2 is CH2CH2Br or CH2CH2I. .
5. The compound of claim 4 wherein R is CH3.
6. The compound of claim 4 wherein R3 is CH2CH2Br.
7. The compound of claim 1 wherein R4 is H.
8. The compound of claim 1 wherein R4 is an alkali metal cation.
9. The compound of claim 1 wherein R4 is (4,4,6trimethyl tetrahydro1,3oxazin2yl)ethyl.
10. The compound of claim 1 wherein R and R taken toge¬ ther with the N atom are morpholino.
11. The compound of claim 1 wherein R2 and R3 taken toge¬ ther with the N atom are piperidinyl.
12. 5Fluoro2'deoxy5'uridyl[2(4, ,6trimethyltetra hydro1 ,3oxazin2yl)ethyl]NmethylN(2bromo ethyl)phosphoramidate.
13. 5Fluoro2*deoxy5'uridyl[2(4,4,6trimethyItetra hydro1,3oxazinyl)ethyl]NmethylN(2chloroethyl) phosphoramidate.
Description:
PHOSPHORAMIDATE ANALOGS OF 5-FLORO-2 ' -DEOXYϋRIDINE

BACKGROUND OF THE INVENTION

The present invention was made with the support o National Cancer Institute grants CA34619 and CA11198. The U.S. Government has certain rights in the invention.

5-Fluorouracil (5-FU) is the antineoplastic agent of choice for the treatment of carcinoma of the pancreas, and, in combination with semustine, is widely used to trea colorectal cancer and gastric cancer. Fluorouracil is als used topically in the treatment of precancerous dermatoses especially actinic keratosis, for which it is the treatmen of choice when multiple lesions occur.

5-FU is a congener of uracil that acts both as a surrogate and as an antimetabolite of that nucleotide. It metabolite, 5-fluorodeoxyuridine-5'-monophosphate (F-dUMP) is a potent inhibitor of thymidylate synthetase, thus blocking the synthesis of thymidylic acid and hence of DNA. The analog 2'-deoxy-5-fluorouridine has been used to treat adenoc rcino a metastatic to the liver. Despite the potency of 5-FU, low response rates, low therapeutic indices, and the development of resistance represent major problems in the clinical application of this drug and its analogs.

Therefore, a need exists for analogs or prodrugs of 5-FU that are both readily taken up by tumor cells whil retaining the ability to inhibit thymidylate synthetase.

SUMMARY OF THE INVENTION The present invention provides a series of phos- phoramidate analogs of 5-fluoro-2'-deoxyuridine of the general formula (I):

wherein R 1 is H, F or (Ct-C 4 )alkyl; R 2 is CH 2 CH 2 X wherein X is Cl, Br, I or p_-toluenesulfonyl; R 3 is (Ci-C A )alkyl or CH 2 CH 2 X wherein X is Cl, Br, I or p_-toluenesulfonyl; or wherein R 2 and R 3 , taken together with the N atom, can be 5- or 6-membered heterocyclic ring which is aliphatic or aliphatic interrupted by a ring oxygen or a second ring nitrogen; R 4 is H, one equivalent of a pharmaceutically- acceptable cation or (4,4,6-trimethyltetrahydro-l,3-oxazi 2-yl)ethyl, and the pharmaceutically-acceptable salts thereof.

Preferably R 1 is F, H, or CH 3 , most preferably R 1 is F. Preferably R is the moiety ( ,4,6-trimethyl- tetrahydro-l,3-oxazin-2-yl)ethyl. Compounds containing this moiety can readily cross cell membranes and are intra cellularly converted into phosphoramidate derivatives wherein R 4 is H. Compounds of the present invention where in R* is (4,4,6-trimethyltetrahydro-l,3-oxazin-2-yl)ethyl are shown on Table I, below.

TAB E I

Concentration of compound required to kill 99% of B16 melanoma cells in a clonogenic assay. Cells were treated with the compound for 2 hr.

It is believed that the present compounds exhibit antitumor and/or antiviral activity at least in part via their ability to inhibit the enzyme thymidylate synthase (TS) . Compounds wherein at least one of R 2 or R 3 is CH 2 CH 2 X, wherein X is a leaving group such as Cl, Br, I, p_-toluenesulfonyl (OTs) or a similar leaving group, can function as irreversible inhibitors of TS, while compounds wherein R 2 and R 3 taken together with the N atom form a 5-6 membered ring can be hydrolyzed intracellularly to release the bioactive nucleotide NucOP0 3 "2 wherein Nuc is the corresponding nucleoside. The inhibition of TS by these analogs is reversible.

Analogs of the general formula NucOP(O) (NR 2 R 3 ) (0 " ) are also within the scope of the invention, since they are believed to represent the reactive intermediates which are formed in situ following uptake of the corresponding oxa- zinylethyl-substituted compounds by the target cells.

The present invention is also directed to a method for the inhibition of thymidylate synthetase (TS) by con- tacting TS with an effective inhibiting amount of one or more compounds of formula I, either in vitro or in vivo. When administered to mammals in vivo, the compounds of formula I can be used to treat conditions which can be ameliorated by the inhibition of TS activity. Such condi- tions include cancers which respond to 5-fluorouracil (5- FU) treatment, such as gastrointestinal cancer, pancreatic cancer, colorectal cancer, malignant insulinoma, primary hepatocellular carcinoma, prostate cancer, bladder cancer, endometrial carcinoma, cervical cancer, breast cancer, ovarian cancer and the like. The present compounds can also act to inhibit viral replication in vivo or in vitro. Generally, the compounds of formula I are about 10-100

times more active than 5-FU, while exhibiting fewer side effects.

The present invention is also directed to novel intermediates which can be employed to prepare the com- pounds of formula I.

DETAILED DESCRIPTION OF THE INVENTION

Compounds la-d are prepared from 5-fluoro-2'- deoxyuridine as outlined on Figure 1, using the reagents and reaction conditions summarized on Table II, below.

TABLE II Step Reaction Conditions Product a Ph 3 CCl, dimethylaminopyridine, pyridine, 80°C, 30 min b t-butyldimethylsilylchloride, imidazole, DMF, 18 hr, 25°C c HOAc-H 2 0, 30 min, reflux 15. f Lithium diisopropyla ide, then 3/7 add to 16a-c, THF, 0° to 25°C, 18 hr. g H0Ac-H 2 0, 80°C, 30 min; then

NaOH h NaI0 4 , pH=5.0, THF i 4-Methyl-4-amino-2-pentanol , _18_

3A molec . sieves., CH 2 C1 2 j Bu NF , THF, 0° la-d

To prepare compounds Jla, .lc and le , step f is carried out using intermediates 16a-c, respectively, which have the general formula (16) :

wherein X is Cl, Br or I, respectively.

Generally, the 3'-protected nucleoside ]5 was prepared by treating the 2'-deoxynucleoside, .14 sequen¬ tially with triphenylmethyl chloride and t-butyldimethyl- silyl chloride " , followed by detritylation. The phosphoryl ating agent was prepared by reaction of phosphorus oxy¬ chloride with the appropriate amine salt followed by treat ment with the lithium salt of 4-(2-hydroxyethyl)-2,2- dimethyl-l,3-dioxolane. The protected nucleoside JL5. was then converted to its alkoxide and phosphorylated with 16. to give 17_. The acetonide was hydrolyzed, the resulting diol was cleaved with sodium periodate, and the resulting aldehyde was trapped with 4-methyl-4-amino-2-pentanol to give 18.. Finally, the 3'-protecting group was removed to give the 2'-deoxynucleotide phosphoramidates La, _l£ or Id. Tosyl analog 16_ was prepared by reacting 2J_, X=Br with silver tosylate in acetonitrile at reflux for 3 hr to yield Y]_ r X=OTs, which was further reacted as described above.

Morpholino analog a_ was prepared by replacing intermediate _16_ with 2-(2,2-dimethyl-l,3-dioxolan-4-yl)- ethyl-morpholino-phosphoramidyl chloride, which was in tur prepared by reacting phosphorus oxychloride sequentially with morpholine and 4-(2-hydro yethyl)-2,2-dimethyl-1,3- dioxolane. Morpholine can be replaced with other hetero¬ cyclic ring compounds, such as piperazine and piperidine t

afford compounds of formula I wherein R 2 and R 3 taken to¬ gether with N are a 5- or 6-membered heterocyclic ring.

. Useful dosages of the compounds of formula I can be determined by comparing their in vitro activity, and in vivo activity in animal models, to that of an equivale dosage of 5-fluorouracil of or of 2'-deoxy-5-fluorouridin both of which are currently employed in the treatment of human cancers. For example, a compound of formula I that is 10-20 times more potent than 5-FU against a particular cancer, such as those discussed above, may be administere intravenously in a single unit dose of about 0.75-1.5 mg/ once a week, for as long as clinical improvement is evi¬ dent. The dosage can be adjusted weekly according to the patient's tolerance. The compounds of the present inven- tion can also be administered orally, as in capsuies or tablets. The present compounds can also be applied topi¬ cally, e.g., in a 1-5% cream or in a 1-5% solution, in combination with a semi-solid emulsified cream base, or i combination with a pharmaceutically-acceptable liquid vehicle.

Pharmaceutically-acceptable cations include alka metal salts (Li + , Na + , K + ) as well as NH A + and other nontox ammonium salts. Pharmaceutically-acceptable salts of the compounds of formula I include nontoxic amine acid additi salts of inorganic acids (HC1, H 2 SO A , H 3 P0 A ) and organic acids, e.g., citrates, tartrates, gluconates, polygluco- nates, malates and the like.

The present compounds of formula I include both the racemic (dl), partially-resolved (optically-active) mixtures of stereoisomers or the fully resolved forms.

Typically, the 1' and 4' bonds of the oxocyclopentane rin will be beta (or above the plane of the ring) and the 3'-

hydroxy group will be alpha (or below the plane of the ring), as depicted hereinabove.

The invention will be further described by refer ence to the following detailed examples in which 31 P NMR spectra were recorded on a Bruker WP-270 SY instrument equipped with a VSP ultinuclear probe tuned for 109.368 MHz using 10 mm sample tubes, 5000Hz spectral width, and 6 acquisitions. Broadband gated decoupling was used, and chemical shifts are reported in parts per million from 5% triphenylphosphine oxide in toluene-d 8 as a coaxial refer¬ ence. *H NMR spectra were recorded on the same instrument using 5 mm sample tubes and 32 acquisitions. Chemical shifts are reported in parts per million from tetramethyl- silane. Elemental analyses were performed by Galbraith

Laboratories, noxville, TN. IR spectra were recorded on Perkin Elmer 1310 Infrared Spectrometer. Melting points were determined on a Mel-Temp apparatus and are uncor- rected. All chromatography refers to flash chromatography over silica gel, and all organic solvents were distilled prior to use unless otherwise specified.

Example 1. N-Methyl-N-(2-bromoethyl)amine, hvdrobromide salt.

This compound was prepared as described previousl by F. Cortese, Orcr. Syn. , 18, 13 (1938), on a 133 mmol scale and isolated as a white solid (20.36g, 70%): p 66-

74°C; *H NMR (CDC1 3 ) 3.83(t, 2H, J = 6.67Hz), 3.47(t, 2H, J = 6.35Hz), 2.82(s, 3H)ρpm; IR ( Br) 3410, 2960, 2750, 2410,

1630, 1590, 1470, 1440, 1310, 1260, 945, 910, 1060, 1015,

960, 945, 870, 805cm "1 .

Example 2. N-Methyl-N-(2-chloroethyl)amine, hydrochlori salt.

Hydrogen chloride was bubbled into a stirred so tion of 2-(methylamino)ethanol (10 g, 133 mmol) in CH 2 C1 2 (25 ml) until the mixture turned wet litmus paper red. mixture was cooled to 0°C, and thionyl chloride (15.82g, 133 mmol) was added dropwise. The mixture was allowed to stir overnight at room temperature. The solvent was re¬ moved under reduced pressure to give product as a white solid (16.60g, 96% yield): mp 95-100°C; : H NMR (DMSO-d 6 ) 4.00(t, 2H, J = 6.28Hz), 3.36(t, 2H, J = 6.29Hz), 2.81(s, 3H)ppm; IR (KBr) 3400, 2960, 2750, 2420, 1730, 1580, 1460 1390, 1310, 1270, 1200, 1150, 1165, 1005, 990, 900, 860, 710cm -1 .

Example 3. N-Methyl-N-(2-iodoethyl)amine, hydriodide sal

This compound was prepared analogously to the bromo analog of Example 1, on a 133 mmol scale. The pro¬ duct was isolated as an off white solid (38.73g, 93% yield): ' mp 134-136 β C; : H NMR (CDC1 3 ) 3.32(m, 4H) , 2.60(s, 3H)ppm; IR (KBr) 3100, 3000, 2960, 2860, 2750, 2710, 2470 1560, 1460, 1450, 1415, 1395, 1350, 1190, 1135, 1100, 107 1050, 1000, 975, 955, 910, 835, 850cm "1 .

Example 4. 4-(2-Hydroxyethyl)-2,2-dimethyl-1,3-dioxolane . .Butane-1,2,4-triol (5.0g, 47 mmol) was dissolved in MeOH (5 ml). Acetone (20 ml), MgS0 A (ca. 500mg) , and para-toluene sulfonic acid (p-TsOH) (catalytic amount) we added, and the mixture was allowed to stir for 5 days at room temperature. The mixture was filtered and the fil¬ trate concentrated under reduced pressure. Methylene chloride (CH 2 C1 2 ) (20 ml) and water (20 ml) were added, th layers were separated, and the organic layer was washed

with water (2 x 20 ml) . The organic layer was dried (MgSO A ) , filtered, and the filtrate concentrated under reduced pressure to afford the product as a clear oil (5.15g, 75%): Η NMR (CDC1 3 ) 4.23(dt, 1H, J = 6.86Hz), 4.04(t, 1H, J = 6.06Hz), 3.72(m, 2H) , 3.54(t, 1H, J = 7.72Hz), 2.55(broad s, 1H) , 1.77(dt, 2H, J = 6.67Hz), 1.34(d, 6H, J = 15.68Hz)ppm; IR (neat) 3420, 2980, 2930, 2870, 1710, 1455, 1370, 1250, 1215, 1155, 1055, 855, 732 cm

Example 5. 4-Methyl-4-amino-2-pentanol♦

5,6-Dihydro-2,4,4,6-tetramethyl-4H-l,3-oxazine (lOg, 70 mmol) was refluxed in 80 ml of 10% aqueous NaOH for 8.5 hr. The mixture was allowed to cool to room tem- perature and was then saturated with NaCl and extracted with ether (5 x 30 ml) . The ether extracts were combined and dried over solid KOH. The solvent was removed under reduced pressure to afford the product as an oil (7.30g, 89%): ^ NMR (CDC1 3 ) 4.06(m, 1H), 1.34(d, 2H, J = 5.54Hz) 1.15(s, 6H), 1.09(d, 3H, J = 7.17Hz)ppm; IR (neat) 3340,

3280, 2960, 2920, 2890, 2870, 1600, 1465, 1440, 1380, 136 1335, 1300, 1260, 1190, 1170, 1130, 1100, 1050, 1000, 970, 900, 875, 835, 760cm "1 .

Example 6. 3 '-0-t-Butyldimethylsilyl-5-£luoro-2 '-deoxy- uridine (15) .

To a solution of 5-fluoro-2'-deoxyuridine (14,

1.0Og, 4.06 mmol) in pyridine (7 ml) was added triphenyl- ethyl chloride (1.25g, 4.47 mmol) and dimethylaminopyri- dine (0.4g, 3.05 mmol). The mixture was allowed to stir a

80°C for 30 min. The pyridine was removed under reduced pressure and the residue dissolved in DMF (4 ml). I ida- zole (0.67g, 9.77 mmol) and t-butyldimethylsilyl chloride

(0.74g, 4.88 mmol) were added, and the mixture was allowed

to stir overnight at room temperature. The DMF was remo under pressure, and the residue was dissolved in 80% aqu ous acetic acid (5 ml). The mixture was allowed to refl for 30 min, cooled, and neutralized with NaOH. The mixt was lyophilized, and the residue was purified by chromat raphy (1:1 EtOAc:hexanes) to give 15 as a white solid (709mg, 48%): mp 138-142°C; R f 0.65 (1:9 MeOH:CH 2 Cl 2 ) ; X NMR (CDC1 3 ) 7.98(d, IH, J = 6.39Hz), 6.23(t, IH, J = 6.78Hz), 4.49(dt, IH, J = 5.56Hz), 3.98(m, 2H) , 3.84(m, IH), 2.26(m, 2H) , 0.90(s, 9H) , 0.10(s, 6H) ; IR (KBr) 346 3190, 3080, 3050, 2930, 2860, 1720, 1655, 1490, 1475, 14 1400, 1335, 1250, 1190, 1120, 1095, 1030, 1005, 950, 910 835, 760, 700, 670, 640cm "1 .

Example 7. T2-(2,2-dimethyl-l,3-dioxolan-4-yl)ethyl]-N- methyl-N-(2-bromoethyl)phosphoramidoyl chloride (16a).

Triethylamine (12.24g, 121mmol) was added dropw to a stirred solution of N-methyl-N-bromoethylamineΗBr

(12.04g, 55 mmol) and phosphorus oxychloride (8.44g, 55 mmol) in CH 2 C1 2 (100 ml) at 0°C under N 2 . The mixture wa allowed to stir overnight and then poured over ice. The layers were separated, and the aqueous layer was extract with CH 2 C1 2 (3 x 100 ml). The organic layers were combin and dried (MgS0 A ) . The filtrate was concentrated under reduced pressure and the residue purified by chromatogra (1:4 EtOAc:hexanes) to give N-methyl-N-(2-bromoethyl)pho phoramidic dichloride as an oil (13g, 93%): R f 0.67 (1:4 EtOAc:hexanes) ; l E NMR (CDC1 3 ) 3.65(dt, 2H, J = 14.10Hz), 3.50(t, 2H, J = 6.52Hz), 2.93(d, 3H, J = 15.46Hz)ppm; 31 P NMR (CDC1 3 ) -6.57ppm; IR (neat) 2980, 2940, 2880, 1740,

1450, 1370, 1340, 1280, 1250, 1210, 1105, 1050, 1005, 98 975, 940, 915, 865, 755, 700cm "1 .

Butyllithium (10.8 ml, 21.60 mmol, 2.0M) was adde dropwise at 0°C to a stirred solution of 4-(2-hydroxyethyl -2,2-dimethyl-l,3-dioxolane (2.87g, 19.60 mmol) and a crys tal of 4-phenylazodiphenylamine indicator in THF (7 ml) under N 2 . The resulting solution was added dropwise at - 78°C to a stirred solution of N-methyl-N-(2-bromoethyl) phosphoramidic dichloride (5.00g, 19.60 mmol) in THF (10 ml) under N 2 . The mixture was allowed to stir under N 2 at -78°C for 3 hr, at which time the purple mixture turned yellow. The mixture was warmed to room temperature and th solvent removed under reduced pressure. The residue was purified by chromatography (1:4 EtOAc: hexanes) and the product 16a isolated as an oil (4.77g, 67%): R f 0.61 (1:1 EtOAc:hexanes) ; X H NMR (CDC1 3 ) 4.26(dt, 2H, J = 8.44Hz), 4.17(t, IH, J = 6.53Hz), 4.06(t, IH, J = 7.06Hz), 3.54(t, IH, J = 7.10Hz), 3.44(m, 4H), 2.76(d, 3H, J = 12.76Hz), 1.95(dt, 2H, J = 6.24Hz), 1.67(d, 6H, 15.63Hz); 31 P NMR (CDC1 3 ) -8.07 ppm.

Example 8. 3 r -Q-t-Butyldimethylsilyl-5-fluoro-2 '-deoxy-5 ' - uridyl-r2-(2,2-dimethyl-l,3-dioxolan-4-yl)ethyl1-N-methyl- N-(2-bromoethyl)phosphoramidate (17, X=Br) .

Lithium diisopropylamide was prepared by adding n- butyllithium (1.38 ml, 2.75 mmol, 2.0M) to a stirred solu- tion of diisopropylamine (0.39 ml, 2.75 mmol) in THF (1 ml) at 0°C under N 2 . The mixture was allowed to stir at 0°C for 10 min. This solution was added dropwise to a stirred solution of 15_ (0.45g, 1.25 mmol) in THF (5 ml) at 0°C under N 2 . This alkoxide solution was then added dropwise to a stirred solution of 16a (0.4g, 1.25 mmol) in THF (5 ml) at 0°C under N 2 , and stirring was continued overnight at room temperature. The solvent was then removed under reduced pressure and the residue purified by chromatography (EtOAc) to give 17., X=Br (0.72g, 71%): R f 0.71 (1:9 MeOH:

CH 2 C1 2 ); : H NMR (CDCI 3 ) 7.82(d, 1/2H, J = 6.41Hz), 7.77(d, 1/2H, J = 6.25Hz), 6.27(m, IH) , 4.44(m, IH) , 4.11(m, 7H) 3.56(5, IH, J = 7.37Hz), 3.46(m, 4H) , 2.72(d, 3H, J = 9.34Hz), 2.30(m, IH) , 2.03(m, IH) , 1.93(m, 2H) , 1.36(d, J = 13.89Hz), 0.87(s, 9H) , 0.08(s, 6H)ppm; 31 P NMR (CDC1 3 14.30, -14.50 ppm.

Example 9. 3 '-O-t-Butyldimethylsilyl-5-fluoro-2'-deoxy- uridyl-f2-( , ,6-trimethyltetrahydro-l,3-oxazin-2- yl)ethγl1-N-methyl-N-(2-bromoethyl)phosphoramidate (18, X=Br) .

Compound J7, X = Br (340mg, 0.50 mmol) was dis¬ solved in 80% aqueous acetic acid (2 ml), heated to 80°C for 30 min, cooled, and neutralized with NaOH. The solu tion was lyophilized, the residue taken up in THF, the salts removed by filtration, and the residue concentrate under reduced pressure to afford the corresponding diol an oil (270mg, 83%): R f 0.54 (1:9 MeOH:CH 2 Cl 2 ) ; 31 P NMR -13.53, -13.93, -14.06ppm. To a solution of the diol (220mg, 0.35 mmol) in THF (3 ml) was added NaIO (8.0mg, 0.39 mmol) in acetate buffer (3 ml, 1M in H 2 0, pH = 5.0). The mixture was allowed to stir for 10 min, and the THF then removed under reduced pressure. The mixture was ly philized, the residue taken up in THF, and the salts fil tered, and the filtrate concentrated under reduced pres¬ sure. The residue was dissolved in CH 2 C1 2 (3ml) and the amino alcohol of Ex. 5 (40mg, 0.35 mmol) in CH 2 C1 2 (2 ml) was added. The mixture was allowed to stir over 3 A° mo cular sieves for 15 min. The sieves were removed and th solvent removed under reduced pressure. The residue was purified by chromatography (2% Me0H:Et0Ac) to afford 18, X=Br (161mg, 65%): R f 0.69 (1:9 MeOH:CH 2 Cl 2 ) ; l E NMR (CDC 7.78(d, 1/2H, J = 6.07Hz), 7.73(d, 1/2H, J = 6.07Hz), 6.23(m, IH), 4.40(m, 2H) , 4.04(m, 5H) , 3.74(m, IH) , 3.43(

4H) , 2. 69 (d, 3H, J = 9 . 17Hz ) , 2. 27 (m, IH) , 2 . 01 (m, IH) , 1.87 (m, 2H) , 1.41(d, IH, J = 13.24Hz ) , 1. 14 (m, 10H) , 0. 85 (s , 9H) , 0. 05 (s , 6H) ; 31 P NMR (CDC1 3 ) -14.30 , -14.52ppm.

Example 10. 5-Fluoro-2'-deoxy-5 / -uridyl-r2-(4,4,β-tri- methyltetrahydro-1,3-oxazin-2-yl)ethyl]-N-methyl-N-(2- bromoethypphosphoramidate (la) .

Tetrabutylammonium fluoride (0.15 ml, 0.15 mmol,

1.0M in THF) was added at 0°C to a stirred solution of 18, X=Br (0.105g, 0.15 mmol) in THF (3 ml). The mixture was allowed to stir for 20 min at 0 C C. The solvent was remove under reduced pressure and the residue purified by chroma¬ tography (3% MeOH:EtOAc) to afford la (33 mg, 37%): R f 0.40 (1:9 MeOH:CH 2 Cl 2 ); X H NMR (CDC1 3 ) 7.79(m, IH) , 6.22(m, IH), 4.51(m, IH) , 4.45(m, IH) , 4.25(m, 5H) , 3.74(m, IH), 3.48(m, 4H), 2.72(d, 3H, J = 9.54Hz), 2.45(m, IH) , 2.16(m, IH), 1.92(m, 2H), 1.43(d, IH, J = 11.60Hz), 1.10(m, 9H), 0.91(d, IH, J = 12.00Hz)ppm, 31 P NMR (CDC1 3 ) -13.29, -13.65, -13.69, -13.81ppm; IR (neat) 3370, 3080, 2960, 2920, 1710, 1660, 1470, 1400, 1350, 1260, 1230, 1090, 1030, 975, 900, 870, 800, 760, 730cm "1 ; LSIMS m/e 601(M + H) + , 623(M + Na) + .

Example 11. 3'-Q-t-Butyldimethylsilyl-5-fluoro-2'-deoxy- 5 -uridyl-r2-(2 r 2-dimethyl-l,3-dioxolan-4-yl)ethyl)-N- methyl-N-(2-tosylethyl)phosphoramidate (17, X=OTs) .

Silver tosylate (1.09g, 3.91 mmol) was added to a solution of 17., X=Br (0.67g, 0.98 mmol) in CH 3 CN (2.5 ml).

The mixture was refluxed for 3 hr. The mixture was cooled, filtered, and the solvent removed under reduced pressure to afford 17, X=OTs as an oil (0.70g, 92%): R f 0.75 (1:9 MeOH:

CH 2 C1 2 ); l E NMR (CDC1 3 ) 7.74(m, 3H), 7.31(d, 2H, J =

8.04Hz), 6.24(m, IH), 4.41(m, IH), 4.00(m, 9H), 3.52(t, IH,

J = 7.31), 3.28(m, 2H) , 2.65(d, 3H, J = 9.34Hz), 2.40(s,

3H), 2.22(m, IH) , 2.02(m, IH), 1.88(m, 2H), 1.32(d, 6H, J =

16.24Hz), 0.84(s, 9H) , 0.05(s, 6H)ppm; 31 P NMR (CDC1 3 ) -13.38, -12.92ppm; LSIMS m/e 780.2(11 + H) + , 802.2(M + Na)

Example 12. 3'-O-t-Butyldimethylsilyl-5-fluoro-2 'deoxy-5 uridyl-f 2-( , ,6-trimethyltetrahydro-l,3-oxazin-2- yl)ethyl1-N-methyl-N-(2-tosylethyl) hosphoramidate (18, X=OTs) .

This compound was prepared as described for 18,

X=Br (0.90 mmol scale). The crude product was purified b chromatography (2% MeOH:EtOAc) to afford 18, X=OTs (333mg 46%): R f 0.73 (1:9 MeOH:CH 2 Cl 2 ) ; : H NMR (CDC1 3 ) 7.86(d, 1/2H, J = 6.16HZ), 7.77(m, 2 1/2H), 7.34(d, 2H, J = 7.81HZ), 6.25(m, IH) , 4.44(m, 2H), 4.11(m, 5H) , 3.93(m, IH), 3.74(m, 2H) , 3.42(m, 2H) , 2.68(d, 3H, J = 9.42HZ), 2.44(s, 3H), 2.26(m, IH) , 2.03(m, IH) , 1.90(m, 2H) , 1.42( IH), 1.13(m, 10H) , 0.88(8, 9H) , 0.08(s, 6H)ppm; 31 P NMR (CDC1 3 ) -14.13, -14.36ppm.

Example 13. 5-Fluoro-2'-deoxy-5'-uridyl-f2-(4,4,6-tri- methyltetrahydro-1,3-oxazin-2-yl)ethyl]-N-methyl-N-(2- tosylethyl)phosphoramidate (lb) .

This compound was prepared as described for La (0.41 mmol scale). The crude product was purified by chr matography (3% MeOH:EtOAc) to give lb (37mg, 13% yield): R f 0.42 (1:9 MeOH:CH 2 Cl 2 ) ; X H NMR (CDC1 3 ) 7.76(m, 3H) , 7.36 (d, 2H, J = 7.75HZ), 6.20(m, IH) , 4.48(m, 2H) , 4.17(m, 6H 3.76(m, 2H), 3.30(m, 2H) , 2.69(d, 3H, J = 9.80Hz), 2.45(s 3H), 2.22(m, IH) , 2.05(m, IH) , 1.94(m, 2H) , 1.40(d, IH, J 12.99Hz), 1.15(m, 9H0, 0.10(d, IH, J = 14.60Hz)ppm; 31 P NM (CDC1 3 ) -13.30, -13.58 ppm; LSIMS calcd for MH + 693.2371; found 693.2385.

Example 14. r2-(2,2-dimethyl-l,3-dioxolan-4-yl)ethyl]-N- methyl-N-(2-chloroethyl)phosphoramidoyl chloride (16b) .

This compound was prepared from N-methyl-N-chlor ethylamine-HCl via N-methyl-N-(2-chloroethyl) hosphoramid dichloride, as described for 16a (14 mmol scale) . The crude residue was purified by chromatography (1:4 EtOAc: hexanes) to give 16b as an oil (2.72g, 61%): R f 0.75 (1:1

EtOAc:hexanes) ; H NMR (CDC1 3 ) 4.22(m, 4H) , 3.60(m, 3H),

3.42(m, 2H), 2.80(d, 3H, J = 12.85Hz), 1.99(dt, 2H, J = 6.11Hz), 1.36(d, 6H, J ' = 15.82Hz)ppm; 31 P NMR (CDC1 3 ) -7.69

-7.92 ppm (1:1 ratio of diastereo ers) .

Example 15. 3 r O-t-Butyldimethylsilyl-5-fluoro-2'-deoxy-5' uridyl- 2-(2,2-dimethyl-l,3-dioxolan-4-yl)ethyl]-N-methyl- N-(2-chloroethyl)phosphoramidate (17, X=C1) .

This compound was prepared as described for 17,

X=Br (1.39 mmol scale) using 16b. The crude residue was purified by chromatography (EtOAc) to give L7, X=C1 (725mg

81%): R f 0.75 (1:9 MeOH:CH 2 Cl 2 ) ; X H NMR (CDC1 3 ) 7.84(d, 1/2H, J = 6.48Hz), 7.77(d, 1/2H, J = 6.32Hz), 6.27(m, IH), 4.43(m, IH) , 4.11(m, 7H), 3.59(m, 3H) , 3.37(m, 2H) , 2.72(d 3H, J = 8.61HZ), 2.28( , IH) , 2.05(m, IH), 1.92(m, 2H) , 1.35(d, 6H, J = 16.21HZ), 0.88(s, 9H) , 0.08(s, 6H)ppm; 31 P NMR (CDC1 3 ) -14.19, -14.44ppm. (1:1 ratio of diastereomers); LSIMS /e 644.2(M + H) + , 666.1(M + Na) + .

Example 16. 3'-0-t-Butyldimethylsilyl-5-fluoro-2'-deoxy- 5 '-uridyl-T2-(4,4,6-trimethyltetrahydro-l,3-oxazin-2- yl)ethyl]-N-methyl-N-(2-chloroethyl)phosphoramidate (18, X=C1) .

This compound was prepared as described for 18,

X=Br (1.13 mmol scale). The crude residue was purified by chromatography (2% MeOH:EtOAc) to afford L8., X=C1 (217mg,

30%): R f 0.73 (1:9 MeOH:CH 2 Cl 2 ) ; l E NMR (CDC1 3 ) 7.81(d, 1/2H, J = 6.32Hz), 7.75(d, 1/2H, J = 6.30Hz), 6.26(m,lH), 4.40(m,

2H), 4.05(m, 5H) , 3.74(m, IH) , 3.60(m, 2H) , 3.36(m, 2H) , 2.71(d, 3H, 9.38Hz), 2.29(m, IH) , 2.03(m, IH) , 1.94(m, 2H 1.42(d, IH, J = 12.77Hz), 1.13(m, 10H) , 0.86(s, 9H) , 0.05 (s, 6H)ρpm; 31 P NMR (CDC1 3 ) -14.20, -14.42 ppm(l:l ratio o diastereomers) .

Example 17. 5-Fluoro-2'-deoxy-5'-uridyl-f2-(4,4,6-tri- methyltetrahydro-1,3-oxazin-yl)ethyl]-N-methyl-N-(2- chloroethyl)phosphoramidate (lc) . This compound was prepared as described for _la

(0.32 mmol scale). The residue was purified by chromatog raphy. (3% MeOH:EtOAc) to afford lc (51mg, 28%): R f 0.43 (1:9 MeOH:CH 2 Cl 2 ): : H NMR (CDC1 3 ) 7.81(d, 1/2H, J = 6.36Hz) 7.72(d, 1/2H, J = 6.39Hz), 6.21(m, IH) , 4.51(m, IH) , 4,40 (m, IH), 4.19(m, 5H) , 3.76(m, IH) , 3.60(m, 2H) , 3.33(m, 2H), 2.74(d, 3H, J = 9.53Hz), 2.45(m, IH) , 2.17(m, IH) , 1.91(m, 2H), 1.43(d, IH, J - 10.84Hz), 1.06(m, 9H) , 0.91( IH, 12.30Hz)ppm; 31 P NMR (CDC1 3 ) -13.60, -13.78 pρm(mixtur of diastereomers); IR (neat) 3400, 3180, 3080, 2960, 2920 2900, 2820, 1710, 1660, 1470, 1400, 1355, 1345, 1320, 126 1200, 1180, 1160, 1090, 1030, 990, 975, 910, 870, 800, 73 645cm "1 ; LSIMS m/e 557.3 (M + H) + .

Example 18. f2-(2,2-dimethyl-l,3-dioxolan-4-yl)ethyl]-N- methyl-N-(2-iodoethyl)phosphoramidoyl chloride (16c).

This compound was prepared using N-methyl-N-2- iodoethylamine»HI via N-methyl-N-(2-iodoethyl)phosphora- midic dichloride, as described for 16a (10 mmol scale).

The crude product was purified by chromatography (1:4 EtOAc:hexanes) which afforded 16c as a pale yellow oil

(2.50g, 61%): R f 0.67 (1:1 EtOAc:hexanes) ; 'H NMR (CDC1 3 )

4.27(m, 3H), 4.10(t, IH, J = 6.52Hz), 3.59(t, IH, J =

7.38Hz), 3.44(m, 2H) , 3.26(t, 2H, J = 7.56Hz), 2.78(d, 3H

J = 12.89Hz), 2.00(dt, 2H, J = 6.02Hz), 1.38(d, 6H, J =

15.48Hz)ppm; 31 P NMR (CDC1 3 ) -8.46, -8.69pρm (1:1 ratio of diastereomers) .

Example 19. 3 f -0-t-Butyldimethylsilyl-5-fluoro-2'-deoxy- 5'-uridyl-f2-(2,2-dimethyl-1,3-dioxolan-4-yl)ethyl]-N- methyl-N-(2-iodoethyl)phosphoramidate (17, X=I) .

This compound was prepared as described for 17,

X=Br (1.10 mmol scale) using 16c. The crude residue was purified by chromatography (EtOAc) to give 17, X=I (503mg 62%): R f 0.70 (1:9 MeOH:CH 2 Cl 2 ) ; X H NMR (CDC1 3 ) 7.80(d,

1/2H, J = 6.30Hz), 7.78(d, 1/2H, J = 6.41Hz), 6.22(dt, IH, J = 6.67Hz), 4.39(m, IH) , 4.08(m, 7H) , 3.53(m, IH) , 3.35( 2H), 3.21(m, 2H) , 2.65(d, 3H, J = 9.54Hz), 2.29(m, IH) , 2.05(m, IH), 1.93(m, 2H) , 1.31(d, 6H, J = 15.38Hz), 0.83(s 9H), 0.04(s, 6H)pρm; 31 P NMR (CDC1 3 ) -14.39, -14.65 ppm (1: ratio of diastereomers) .

Example 20. 3'-0-t-Butyldimethylsilyl-5-fluoro-2'deoxy-5' uridyl-f2-(4,4,β-trimethyltetrahydro-l,3-oxazin-2-yl)- ethyl]-N-methyl-N-(2-iodoethyl)phosphoramidate (18, X=I) .

This compound was prepared as described for 18,

X=Br (0.68 mmol scale). The crude residue was purified by chromatography (2% MeOHrEtOAc) to afford 18., X-I (166mg,

32%): R f 0.73 (1:9 MeOH:CH 2 Cl 2 ) ; l H NMR (CDC1 3 ) 7.75(d, 1/2H, J = 6.33Hz), 7.71(d, 1/2H, J = 6.25Hz), 6.17(m, IH) , 4.33(m, 2H), 4.03(m, 5H) , 3.66(m, IH) , 3.32(m, 2H) , 3.22(m 2H), 2.60(d, 3H, J = 9.41Hz), 2.26(m, IH) , 2.03(m, IH) , 1.87(m, 2H), 1.34(d, IH, J = 12.32Hz), 1.08(m, 10H) , 0.78 (s, 9H)ppm; 31 P NMR (CDC1 3 ) -14.52, -14.77, -15.06, -15.31 ppm (mixture of diastereomers).

Example 21. 5-Fluoro-2 ' deoxy-5 ' -uridyl- f 2- (4,4, 6-trimeth- yltetrahydro-l,3-oxazin-2-yl) ethyl 1 -N-methyl-N- (2-iodo- ethyl) phosphoramidate (Id) .

This compound was prepared as described for la (0.22mmol). The crude residue was purified by chromatog raphy (3% MeOH:EtOAc) to afford Id (40mg, 28%): R f 0.34 (1:9 MeOH:CH 2 Cl 2 ); X H NMR (CDCL 3 ) 7.74(m, IH), 6.18(m, IH) 4.48(m, IH), 4.45(m, IH) , 4.19(m, 5H) , 3.72(m, IH), 3.34 2H), 3.26(m, 2H) , 2.65(d, 3H, 9.36Hz), 2.40(m, IH) , 2.14 IH), 1.94(m, 2H), 1.44(d, IH, 11.54Hz), 1.12(m, 10H)ppm; 31 P NMR (CDC1 3 ) -13.75, -14.04 ppm (1:1 ratio of diatere- omers); IR (neat) 3380, 3050, 2960, 2920, 2820, 1710, 16 1465, 1400, 1355, 1320, 1260, 1240, 1275, 1090, 1030, 10 975, 940, 900, 870, 800, 735, 700cm "1 ; LSIMS calcd for MH 649.1299; found 649.1315.

Example 22. r2-(2,2-dimethyl-l,3-dioxolan-4-yl)ethyl]- morpholinophosphoramidoyl chloride (16d) .

To a stirred solution of phosphorus oxychloride

(17.63g, 115 mmol) in CH 2 C1 2 (100 ml) at 0°C, under N 2 was added morpholine (lO.OOg, 115 mmol) in CH 2 C1 2 (30 ml). T mixture was allowed to stir overnight, under N 2 , at- room temperature. The mixture was poured over ice, the layers separated, and the aqueous layer extracted with CH 2 C1 2 (3 100 ml). The organic layers were combined, dried (MgS0 A ) filtered, and the filtrate concentrated under reduced pre sure. The residue was purified by chromatography (1:4 EtOAc:hexanes) to give morpholinophosphoramidic dichlori as a clear oil (16.04g, 68%): R f 0.70 (1:4 EtOAc:hexane) : H NMR (CDC1 3 ) 3.71(m, 4H) , 3.30(m, 4H)ppm; 31 P NMR (CDC1 3 ) -8.34ppm; IR (neat) 2970, 2920, 2860, 1455, 1370, 1345, 1300, 1275, 1260, 1140, 1115, 1090, 1070, 1015, 970, 915, 850, 710cm "1 .

16d was prepared using 2Λ_ as described for 16a ( mmol scale) . The crude residue was purified by chromato¬ graphy (1:4 EtOAc:hexanes) to give 16d as a yellow oil

(3.45g, 55%): R f 0.54 (1:1 EtOAc:hexanes) ; X H NMR (CDC1 3 ) 4.27(m, 2H); 4.16(m, IH) ; 4.05(t, IH, J = 7.23Hz), 3.67(m, 4H), 3.54(t, IH, J = 7.18Hz), 3.13(m, 4H) , 1.96(m, 2H) , 1.32(d, 6H, J = 16.36Hz)ρpm; 1 P NMR (CDC1 3 ) ; IR(neat) 2980 2920, 2850, 1710, 1455, 1370, 1330, 1300, 1275, 1260, 1215 1160, 1140, 1110, 1095, 1055, 975, 920, 850, 715cm" 1 .

Example 23. 3 r -Q-t-Butyldimethylsilyl-5-£luoro-2'deoxy-5' uridyl-r2-(2,2-dimethyl-l,3-dioxolan-4-yl)ethyl]-morpho- linophosphoramidate (19) .

This compound was prepared as described for (17

X=Br) (1.2 mmol scale) . The crude residue was purified by chromatography (EtOAc) to give L9_ (492mg, 68%): R f 0.72

(1:9 MeOH:CH 2 Cl 2 ); X H NMR (CDC1 3 ) 7.76(d, 1/2H, J = 6.31Hz), 7.71(d, 1/2H, J = 6.27Hz), 6.22(m, IH), 4.38(m, IH), 4.06 (m, 6H), 3.88(m, IH) , 3.62(m, 4H) , 3.54(5, IH, J = 7.00Hz) 3.11(m, 4H), 2.25(m, IH) , 2.01(m, IH) , 1.88(m, 2H) , 1.32(d 6H, J = 18.20Hz), 0.84(s, 9H) , 0.05(s, 6H)ppm; 31 P NMR (CDC1 3 ) -16.15, -16.47 ppm (1:1 ration of diastereomers); LSIMS m/e 638(M + H) + ; 660(M + Na) + .

Example 24. S'-O-t-Butyldimethylsilyl-S-fluoro-Σ'deoxy-S'- uridyl-T -(4, ,6-trimethyltetrahydro-l,3-oxazin-2-yl)- ethyl]-morpholinophosphoramidate (20) . This compound was prepared as described for 18,

X=Br (0.81 mmol scale) using .19.. The crude product was purified by chromatography (2% MeOH:EtOAc) to give 2O (178 mg, 33%): R f 0.70 (1:9 MeOH:CH 2 Cl 2 ); X H NMR (CDC1 3 ) 7.78(d, 1/2H, J = 6.15Hz), 7.73(d, 1/2H, J = 6.06Hz), 6.23(m, IH), 4.38(m, 2H), 4.07(m, 5H) , 3.71(m, IH) , 3.63(m, 4H) , 3.12(m, 4H), 2.27(m, IH), 2.02(m, IH) , 1.89(m, 2H) , 1.41(d, IH, J = 13.08), 1.07(m, 10H) , 0.86(s, 9H) , 0.06(s, 6H)ppm; 31 P NMR (CDC1 3 ) -16.08, -16.39 ppm (1:1 ratio ' of diastereomers); IR (neat) 3400, 2860, 2820, 2850, 1710, 1660, 1465, 1400, 1355, 1255, 1190, 1110, 1090, 1020, 975, 910, 830, 775cm" 1 .

Example 25. 5-Fluoro-2'-deoxy-5'-uridyl- 2-(4,4,6-tri- methyltetrahydro-l,3-oxazin-2-yl)ethyl]-morpholinophos- phoramidate (le) . This compound was prepared as described for .la

(0.27 mmol scale). The crude residue was purified by chr matography (3% MeOH:EtOAc) to give Le (65 mg, 44%): R f 0.36 (1:9 MeOH:CH 2 Cl 2 ) ; : H NMR (CDC1 3 ) 7.70(d, 1/2H, J = 6.11Hz), 7.64(d, 1/2H, J = 6.13Hz), 6.15(m, IH) , 4.40(m, 2H), 4.08(m, 5H) , 3.70(m, IH) , 3.59(m, 4H) , 3.08(m, 4H) , 2.36(m, IH), 2.02(m, IH) , 1.88(m, 2H) , 1.39(d, IH, J = 13.04Hz), 1.16(m, 10H)ppm; 31 P NMR (CDC1 3 ) -15.42, -15.71, -15.83 ppm (mixture of diastereomers); IR (neat) 3400, 3080, 2960, 2850, 1710, 1650, 1470, 1450, 1400, 1350, 1260 1100, 1030, 975, 910, 800, 730cm "1 ; LSIMS m/e 551(M + H) + .

Example 26. Preparation of Bis(2-bromoethyl)amine, hydro- bromide salt. Ice cold diethanol amine (lOg, 95 mmol) was added dropwise to a stirred solution of hydrobromic acid (37.6g, 464 mmol) at 0°C. The mixture was allowed to re¬ flux and H 2 0 was distilled off at 1 hr intervals (26, 4, 4 4, 4, 1, 1 ml) . The mixture was refluxed for 3 hr, and then H 2 0 (29 ml) was distilled off. The yellow residue wa poured into a beaker, while hot, containing acetone (30 ml). The product was allowed to crystallize out at 0°C an isolated as a white solid (17.37g, 59%); H NMR (DMSO-d 6 ) 3.72(t, 4H, J = 6.70Hz), 3.48(t, 4H, 6.73Hz), 3.09(br.s, lH)ppm.

Example 27. Preparation of 3'-O-t-Butyldimethylsilyl thy- midine 21. To a solution of thymidine (lO.OOg, 41 mmol) i pyridine (50 ml) was added triphenylmethyl chloride (13.81g, 50 mmol) and dimethylaminopyridine (0.4g, 3.0 mmol) . The mixture was allowed to stir at 80°C for 30 min

The pyridine was removed under reduced pressure and the residue dissolved in DMF (80 ml). Imidazole (6.14g, 90 mmol) and t-butyldimethylsilyl chloride (6.18g, 41 mmol) were added, and the mixture was allowed to stir overnight at room temperature. The DMF was removed under reduced pressure, and the residue was dissolved in 80% aqueous acetic acid (60 ml). The mixture was allowed to reflux fo 30 min, cooled, and neutralized with NaOH. The mixture w lyophilized, and the residue was purified by chromatograp (1:1 EtOAc: hexanes) to give T as a white solid (10.35g, 71%): mp 60°C (softens), 90°C (melts); R f 0.69 (1:9 MeOH:CH 2 Cl 2 ); X H NMR (CDC1 3 ) 7.33(m, IH) , 6.13(t, IH, J = 6.75Hz), 4.48(m, IH) , 3.90(m, 2H), 3.74(m, IH) , 2.32(m, IH), 2.22(m, IH) , 1.89(s, 3H) , 0.88(s, 9H) , 0.07(s, 6H)ppm

Example 28. Preparation of 3'-0-t-Butyldimethylsilyl-2'- deoxyuridine 22. To a solution of 2 '-deoxyuridine (5.00g, 22 mmol) in pyridine (20 ml) was added triphenylmethyl chloride (6.72g, 24 mmol) and dimethylaminopyridine (0.20g 1.6 mmol). The mixture was allowed to stir at 80°C for 30 min. The pyridine was removed under reduced pressure and the residue dissolved in DMF (30 ml). Imidazole (3.59g, 5 mmol) and t-butyldimethylsilyl chloride (3.92g, 26 mmol) were added, and the mixture was allowed to stir overnight at room temperature. The DMF was removed under reduced pressure, and the residue was dissolved in 80% aqueous acetic acid (20 ml) . The mixture was allowed to reflux fo 30 min, cooled, and neutralized with NaOH. The mixture was lyophilized, and the residue was purified by chromatograph (1:1 EtOAc: hexanes) to give . as a white solid (3.13g, 9.14 mmol, 41.51% yield): mp 140°C (softens), 160-170°C (melts); R f = 0.65 (1:9 MeOH:CH 2 Cl 2 ); l E NMR (CDC1 3 ) 7.62(d, IH, J = 6.87Hz), 6.16(t, IH, J = 6.61), 5.73(d, IH, J =

5 . 70Hz ) , 4 . 49 (m, IH) , 3 . 93 (m, 2H) , 3 . 76 (m, IH) , 2 . 30 (m, IH) , 2 . 19 (m, IH) , 0 . 89 ( s , 9H) , 0 . 09 ( s , 6H)ppm .

Example 29. Preparation of 3'-O-t-Butyldimethylsilyl thy midyl-r-2-(2,2-dimethyl-l,3-dioxolan-4-yl)] N-methyl-N-(2 bromoethyl phosphoramidate (2-5.) . Lithium diisopropylamid was prepared by adding butyllithium (5.50 ml, 11 mmol, 2.0M) to a stirred solution of diisopropylamine (1.54 ml, 11 mmol) in THF (1 ml) at 0°C. The mixture was allowed t stir at 0°C for 10 min. This alkoxide solution was added dropwise to a stirred solution of 2_1 (1.77g, 4.99 mmol) i the THF (8 ml) at 0 C C. This alkoxide solution was then added dropwise to a stirred solution of 16a (2.00g, 5.48 mmol) in THF (7 ml) at 0 β C and stirring was continued ove night at room temperature. The solvent was then removed under reduced pressure and the residue purified by chroma tography (EtOAc) to give 25. (1.75g, 51%): R f 0.75 (1:9 MeOH:CH 2 Cl 2 ) .

Example 30. Preparation of 3'-Q-t-Butyldimethylsilyl-2'- deoxy-5'-uridyl-r-2-(2,2-dimethyl-l,3-dioxolan-4-yl)]-N- methyl-N-(2-bromoethyl) phosphoramidate 26). Lithium diisopropylamide was prepared by adding butyllithium (1.6 ml, 3.21 mmol, 2.0M) to a stirred solution of diisopropyl amine (0.45 ml, 3.21 mmol) in THF (2 ml) at 0°C. The mix ture was allowed to stir at 0°C for 10 min. This solutio was added.dropwise to a stirred solution of 22. (0.500g, 1.46 mmol) in THF (5 ml) at 0°C. This alkoxide solution was then added dropwise to a stirred solution of 16a (0.532g, 1.46 mmol) in THF (6 ml) at 0°C and stirring was continued overnight at room temperature. The solvent was then removed under reduced pressure and the residue puri-

fied by chromatography (EtOAc) to give 2jS (718 mg, 73%): 0.75 (1:9 MeOH:CH 2 Cl 2 ) .

Example 31. Preparation of 3 -0-t-Butyldimethylsilyl thy midyl-r2-(4,4,β-trimethyltetrahydro-1,3-oxazin-2-yl)ethyl N-methyl-N-(2-bromoethyl)phosphoramidate (27) . Compound (1.72g, 2.52 mmol) was dissolved in 80% aqueous acetic ac (7 ml), heated to 80°C for 30 min, cooled, and neutralize with NaOH. The solution was lyophilized, the residue tak up in THF, the salts removed by filtration, and the resid concentrated under reduced pressure to afford the diol as an oil (l.OOg, 62%): R f 0.50 (1:9 MeOH:CH 2 Cl 2 ) ; 31 P NMR -13.97, -14.10 ppm (mixture of diastereomers). To a solu tion of the diol (855 mg, 1.30 mmol) in THF (3 ml) was added NaI0 (164 mg, 0.77 mmol) in acetate buffer (5 ml, I in H 2 0, pH = 5.0). The mixture was allowed to stir for 10 min, and the THF was then removed under reduced pressure. The mixture was lyophilized, the residue taken up in THF, the salts filtered, and the filtrate concentrated under reduced pressure. The residue was dissolved in CH 2 C1 2 (5 ml) and 4-amino-4-methyl-2-pentanol (125 mg, 1.06 mmol) i CH 2 C1 2 (3 ml) was added. The mixture was allowed to stir over 3 A. molecular sieves for 10 min. The sieves were removed and the solvent removed under reduced pressure. The residue was purified by chromatography (2% MeOH:EtOAc) to give 21_ (364 mg, 48%): R f 0.72 (1:9 MeOH: CH 2 C1 2 ) .

Example 32. Preparation of 3 '-O-t-Butyldimethylsilyl-2'- deoxy-5'-uridyl-f2-( , ,6-trimethyltetrahydro-l,3-oxazin-2 yl)ethyl]-N-methyl-N-(2-bromoethyl)phosphoramidate 28. Compound 2_6_ (718 mg, 1.07 mmol) was dissolved in 80% aqueous acetic acid (3.5 ml), heated to 80°C for 30 min, cooled, and neutralized with NaOH. The solution was lyo-

philized, the residue taken up in THF, the salts removed filtration, and the residue concentrated under reduced pressure to afford the diol as an oil (440 mg, 65%); R f 0.53 (1:9 MeOH:CH 2 Cl 2 ); 31 P NMR -13.70, -13.90, -14.25 ppm (mixture of diastereomers). To a solution of the diol(440 mg, 0.70 mmol) in THF (3 ml) was added NaI0 (164 mg, 0.77 mmol) in acetate buffer (5 ml, IM in H 2 0, pH = 5.0). The mixture was allowed to stir for 10 min, and the THF was then removed under reduced pressure. The mixture was lyo- philized, the residue taken up in THF, the salts filtered, and the filtrate concentrated under reduced pressure. The residue was dissolved in CH 2 C1 2 (5 ml) and the 4-amino-4- methyl-2-pentanol (82 mg, 0.70 mmol) in CH 2 C1 2 (3 ml) was added. The mixture was allowed to stir over 3 A molecular sieves for 10 min. The sieves were removed and the solven removed under reduced pressure. The residue was purified by chromatography (2% MeOH:EtOAc) to give 2. (203 mg, 42%) R f = 0.71 (1:9 MeOH:CH 2 Cl 2 ) .

Example 33. Preparation of Thymidyl-f2-(4,4,- trimethyltetrahydro-1,3-oxazin-2-yl)ethyl]-N-methyl-N-(2- bromoethyl)phosphoramidate (2) . Tetrabutyla monium fluor¬ ide (0.48 ml, 0.48 mmol, 1.0M in THF) was added at 0°C to stirred solution of 1 (344 mg, 0.48 mmol) in THF (5 ml). The mixture was allowed to stir for 30 min at 0°C. The solvent was removed under reduced pressure and the residue purified by chromatography (3% MeOH:EtOAc) to give 7. ( 76 mg, 0.13 mmol, 26% yield): R f = 0.42 (1:9 MeOH:CH 2 Cl 2 ) ; l E NMR (CDC1 3 ) 7.39(m, IH) , 6.25(m, IH) , 4.53(m, IH) , 4.39(m, IH), 4.15(m, 5H) , 3.77(m, IH) , 3.43(m, 4H) , 2.73(d, 3H, J 9.62Hz), 2.41(m, IH) , 2.17(m, IH) , 1.98(m, 5H) , 1.44(d, IH J = 13.4Hz), 1.13(m, 9H) , 1.08(d, IH, J = 13.00Hz)ppm.

Example 34. Preparation of 2 r -Deoxy-5'-uridyl-r2-(4,4,- trimethyltetrahydro-1,3-oxazin-2-yl)ethyl]-N-methyl-N-(2- bromoethyl)phosphoramidate(5.) , Tetrabutylammonium fluoride (0.28 ml, 0.28 mmol, 1.0M in THF) was added at 0 β C to a stirred solution of 28. (193 mg, 0.28 mmol) in THF (2 ml). The mixture was allowed to stir for 45 min at 0°C. The solvent was removed under" reduced pressure and the residue purified by chromatography (3% MeOH:EtOAc) to give 5. (24 mg, 15%): R f = 0.38 (1:9.MeOH:CH 2 Cl 2 ) ; X H NMR (CDC1 3 ) 7.66(m, IH), 6.20(m, IH) , 5.74(d, IH, J = 6.89Hz), 4.56(m, IH) ,

4.41(m, IH), 4.13(m, 5H), 3.56(m, IH) , 3.43(m, 4H) , 2.72(d, 3H, J = 9.51Hz), 2.37(m, IH) , 2.07(m, IH) , 1.81(m, 2H) , 1.79(d, IH, J = 15.58Hz), 1.09(m, 10H) .

Example 35. Preparation of Bis(2-bromoethyl)phosphoramidic dichloride (29) . TEA (7.12g, 70 mmol) was added dropwise to a stirred solution of bis(2-bromoethyl)amine hydrobro- mide (lO.OOg, 32 mmol) and phosphorus oxychloride (4.91g, 32 mmol) in CH 2 C1 2 (50 ml) at 0°C under N 2 . The mixture was allowed to stir overnight and then poured over ice. The ' layers were separated, and the aqueous layer was extracted with CH 2 C1 2 (3 x 50 ml) . The organic layers were combined and dried (MgS0 ) . The filtrate was concentrated under reduced pressure and the residue purified by chromatography (1:4 EtOAc: hexanes) to give 2 as an oil (3.86g, 35%); *H NMR (CDC1 3 ) 3.70 (t, 4H, 6.73Hz), 3.55 (t, 4H, 6.75Hz)ppm.

Example 36. Preparation of 2-(2,2-dimethyl-l,3-dioxolan- 4-yl)ethyl]-bis-(2-bromoethyl)phosphoramidoyl chloride (2fl) . Butyllithium (6.57 ml, 13 mmol, 2.0M) was added dropwise at 0°C to a stirred solution of 4-(2-hydroxy- ethyl)-2,2-dimethyl-l,3-dioxolane (1.75g, 12 mmol) and a crystal of phenylazodiphenylamine indicator in THF (6 ml).

The resulting solution was added dropwise at -78°C to a stirred solution of 29. (4.16g, 12 mmol) in THF (7 ml). T mixture was allowed to stir at -78°C for 3 hr, at which time the purple mixture turned yellow. The mixture was warmed to room temperature and the solvent was removed under reduced pressure. The residue was purified by chro atography (1:4 EtOAc: hexanes) to give .30. as an oil (3.55 65%): R f 0.74 (1:1 EtOAc: hexanes); *H NMR (CDC1 3 ) 4.33(m, 2H), 4.20(m, IH) , 4.11 (t, IH, J = 7.13Hz), 3.56(m, 9H) , 2.05(m, 9H), 2.05(m, 2H) , 1.39(d, 6H, J = 15.75Hz)ppm.

Example 37. Preparation of 3"-O-t-Butyldimethylsilyl-S- fluoro-2'-deoxy-5'-uridyl-T -(2,2-dimethyl-l,3-dioxolan-4 yl)ethyl]-bis-(2-bromoethyl)phosphoramidate ,3 ^ 1 . Lithiu diisopropylamide was prepared by adding butyllithium (1.7 ml, 3.39 mmol, 2.0M) to a stirred solution of diisopropyl amine (0.48 ml, 3.39 mmol) in THF (1 ml) at 0°C. The mix ture was allowed to stir at 0°C for 15 min. This solutio was added dropwise to a stirred solution of 15. (500 mg, 1.54 mmol) in THF (5 ml) at 0°C. This alkoxide solution was then added dropwise to a stirred solution of 3_0. (704 mg, 1.54 mmol) in THF (5 ml) at 0°C and stirring was con¬ tinued overnight at room temperature. The solvent was th removed under reduced pressure and the residue purified b chromatography (EtOAc) to give 3_1 (931 mg, 81%): R f 0.70

(1:9 MeOH: CH 2 C1 2 ) ; ^ NMR (CDC1 3 ) 7.68(m, IH) , 6.25(m, IH) 4.46(m, IH) , 4.18(m, 7H) , 3.57(m, IH) , 3.45(m, 8H) , 2.30( IH), 2.18(m, IH), 1.92(m, 2H) , 1.37(d, 6H, J = 13.7Hz), 0.89(s, 9H) , 0.08(s, 6H)ppm.

Example 38. Preparation of 3'-O-t-Butyldimethylsilyl- thvmidyl-r2(2,2-dimethyl-l,3-dioxolan-4-yl)ethyl]bis-(2- bromoethyl)phosphoramidate (32) . Lithium diisopropylamide

was prepared by adding butyllithium (2.00 ml, 4.00 mmol, 2.0M) to a stirred solution of diisopropylamine (0.56 ml, 4.00 mmol) in THF (1 ml) at 0°C. The mixture was allowed to stir at 0°C for 15 min. This solution was added drop- wise to a stirred solution of 2_1 (647 mg, 1.82 mmol) in TH (3 ml) at 0°C. THis alkoxide solution was then added drop wise to a stirred solution of 3J (l.OOg, 2.18 mmol) in THF (5 ml) at 0°C and stirring was continued overnight at room temperature. The solvent was then removed under reduced pressure and the residue purified by chromatography (EtOAc) to give 3. (972 mg, 69%): R f 0.71 (1:9 MeOH: CH 2 C1 2 ); X H NMR (CDC1 3 ) 7.34(m, IH), 6.24(dt, IH, J = 6.36Hz), 4.36(m, IH) , 4.06(m, 7H), 3.50(m, IH) , 3.40(m, 8H) , 2.18(m, IH), 2.07(m, IH), 1.85(m, 5H), 1.28(d, 6H, J = 14.49Hz), 0.82(s, 9H) , 0.02(s, 6H)ppm. .

Example 39. Preparation of 3 -O-t-Butyldimethylsilyl-2'- deoxy-5 -uridyl-f2-(2,2-dimethyl-l,3-dioxolan-4-yl)ethyl]- bis-(2-bromoethyl)phosphoramidate (33) . Lithium diiso- propylamide was prepared by adding butyllithium (1.60 ml, 3.21 mmol, 2.0M) to a stirred solution of diisopropylamine (0.45 ml, 3.21 mmol) in THF (1 ml) at 0°C. The mixture was allowed to stir at 0°C for 15 min. This solution was added dropwise to a stirred solution of (500 mg, 1.46 mmol) in THF (5 ml) at 0°C. This alkoxide solution was then added dropwise to a stirred solution of 3_0_ (668 mg, 1.46 mmol) in THF (5 ml) at 0°C and stirring was continued overnight at room temperature. The solvent was then removed under re¬ duced pressure and the residue purified by chromatography (EtOAc) to give 3_3_ (765 mg, 68%): R f 0.75 (1:9 MeOH: CH 2 C1 2 ) .

Example 40. Preparation of 3'-O-t-Butyldimethylsilyl-5- fluoro-2'-deoxy-5'-uridyl- * 3, -(dihydroxy)butyl]-bis-(2- bromoethyl)phosphoramidate (34) . Compound 3J. (931 mg, 1. mmol) was dissolved in 80% aqueous acetic acid (5 ml), heated to 80 C C for 30 min, cooled, and neutralized with NaOH. The solution was lyophilized, the residue taken up in THF, the salts removed by filtration, and the residue concentrated under reduced pressure. The crude residue w purified by chromatography (3% MeOH:EtOAc) to give 3_4. (52 mg, 60%): R f 0.60 (1:9 MeOH: CH 2 C1 2 ) .

Example 41. Preparation of 3'-O-t-Butyldimethylsilyl- thymidyl-'3, -(dihydroxy)butyl]-bis-(2-bromoethyl)phospho amidate (35,) . Compound 3_2 (1.41g, 1.47 mmol) was dissolv in 80% aqueous acetic acid (3 ml), heated to 80°C for 30 min, cooled, and neutralized with NaOH. The solution was lyophilized, the residue taken up in THF, the salts remov by filtration, and the residue concentrated under reduced pressure. The crude residue was purified by chromatograp (3% MeOH:EtOAc) to give 3_5 (630 mg, 60%): R f 0.57 (1:9 MeOH: CH 2 C1 2 ); : H NMR (CDC1 3 ) 7.32(d, IH, J = 6.73Hz), 6.15(m, IH), 4.37(m, IH) , 4.17(m, 5H) , 4.00(m, IH) , 3.85( IH) , 3.63(m, IH) , 3.44(m, 8H) , 2.24(m, IH) , 2.16(m, IH) , 1.92(s, 3H), 1.78(m, 2H) , 0.88(s, 9H) , 0.09(s, 6H)ppm.

Example 42. Preparation of 3'-O-t-Butyldimethylsilyl-2'- deoxy-5'-uridyl-f3,4-(dihydroxy)butyl]-bis-(2-bromoethyl)- phosphoramidate (36) . Compound 3_3 (765g, 1.00 mmol) was dissolved in 80% aqueous acetic acid (5 ml), heated to 80° for 30 min, cooled, and neutralized with NaOH. The solu¬ tion was lyophilized, the residue taken up in THF, the salts removed by filtration, and the residue concentrated under reduced pressure. The crude residue was purified by

chromatography (3% MeOH:EtOAc) to give 36. (545 mg, 75%): R 0.58 (1:9 MeOH: CH 2 C1 2 ) .

Example 43. Preparation of 5-Fluoro-2'-deoxy-5'-uridyl- * (4,4,g-trimethyltetrahydro-1,3-oxazin-2-yl)ethyl]bis-(2- bromoethyl)phosphoramidate (3.) . To a stirred solution of 34 (255 mg, 0.36 mmol) in CH 3 CN (4.8 ml) was added aqueous HF (0.25 ml, 50% in H 2 0) . The mixture was allowed to stir for 1 hr and was then neutralized with NaOH. The solution was lyophilized, the residue taken up in THF, the salts removed by filtration, and the filtrate concentrated under reduced pressure to afford the triol (163 mg, 73%): R f 0.36 (1:9 MeOH: CH 2 C1 2 ) . To a solution of the triol (163 mg, 0.26 mmol) in THF (3 ml) was added sodium periodate in aqueous acetate buffer (3 ml, pH = 5.0, IM) . The mixture was allowed to stir for 7 min, and the THF was then removed under reduced pressure. The solution was lyophilized, the residue taken up in THF, the salts filtered, and the fil¬ trate concentrated under reduced pressure. The residue was dissolved in CH 2 C1 2 (5 ml) and 4-amino-4-methyl-2-pentanol (31 mg, 0.26 mmol) in CH 2 C1 2 (3 ml) was added. The mixture was allowed to stir over 3 A molecular sieves for 15 mins. The sieves were removed under reduced pressure. The resi¬ due was purified by chromatography (3% MeOH: EtOAc) to give 9. (17 mg, 10%): R f 0.47 (1:9 MeOH CH 2 C1 2 ) .

Example 44. Preparation of Thymidyl-f2-(4,4,6-trimethyl- tetrahydro-l,3-oxazin-2-yl)ethyl]bis-(2-bromoethyl)phos- phoramidate (fl.) . To a stirred solution of 3_5_ (667 mg, 0.90 mmol) in CH 3 CN (4.75 ml) was added aqueous HF (0.25 ml, 50% in H 2 0) . The mixture was allowed to stir for 1.5 hr and was then neutralized with KOH. The solution was lyophi¬ lized, the residue taken up in THF, the salts removed by

filtration, and the filtrate concentrated under reduced pressure to afford the triol (393 mg, 70%): R f 0.33 (1:9 MeOH: CH 2 C1 2 ) . To a solution of the triol (393 mg, 0.63 mmol) in THF (3 ml) was added sodium periodate in aqueous acetate buffer (3 ml, pH = 5.0, IM) . The mixture was allowed to stir for 8 min, and the THF was then removed under reduced pressure. The solution was lyophilized, the residue taken up in THF, the salts filtered, and the fil¬ trate concentrated under reduced pressure. The residue wa dissolved in CH 2 C1 2 (4 ml) and 4-amino-4-methyl-2-pentanol (59 mg, 0.50 mmol) in CH 2 C1 2 (3 ml) was added. The mixture was allowed to stir over 3 A molecular sieves for 10 ins. The sieves were removed under reduced pressure. The resi¬ due was purified by chromatography (3% MeOH: EtOAc) to giv 1 (167 mg, 48%): R f 0.50 (1:9 MeOH: CH 2 C1 2 ) ; X H NMR (CDC1 3 ) 7.38(d, IH, J = 15.55Hz), 6.23(m, IH) , 4.50(m, IH) , 4.43(m IH), 4.19(m, 4H), 4.06(m, IH), 3.79(m, IH) , 3.44(m, 8H) , 2.64(m, IH), 2.28(m, IH) , 1.93(m, 5H) , 1.45(d, IH, J = 13.71Hz), 1.15(m, 10H)ppm.

Example 45. Preparation of 2'-Deoxy-5'-uridyl- * 2-(4, ,6- trimethyltetrahydro-1,3-oxazin-2-yl)ethyl]-bis-(2-bromo- ethyl)phosphoramidate (£) . To a stirred solution of 3_6_ (545 mg, 0.70 mmol) in CH 3 CN (4.75 ml) was added aqueous HF (0.25 ml, 50% in H 2 0) . The mixture was allowed to stir for 1.5 hr and was then neutralized with KOH. The solution wa lyophilized, the residue taken up in THF, the salts remove by filtration, and the filtrate concentrated under reduced pressure to afford the triol (323 mg, 76%); R f 0.33 (1:9 MeOH: CH 2 C1 2 ) . To a solution of the triol (323 mg, 0.53 mmol) in THF (3 ml) was added sodium periodate in aqueous acetate buffer (3 ml, pH = 5.0, IM) . The mixture was allowed to stir for 10 min, and the THF was then removed

under reduced pressure. The solution was lyophilized, the residue taken up in THF, the salts filtered, and the fil¬ trate concentrated under reduced pressure. The residue wa immediately dissolved in CH 2 C1 2 (10 ml) and 4-amino-4- methyl-2-pentanol (62 mg, 0.53 mmol) in CH 2 C1 2 (5 ml) was added. The mixture was allowed to stir over 3 A molecular sieves for 10 ins. The sieves were removed under reduced pressure. The residue was purified by chromatography (3% MeOH: EtOAc) to give 6. (120 mg, 33%): R £ 0.53 (1:9 MeOH: CH 2 C1 2 ) .

Example 46. Preparation of 3 -O-t-Butyldimethylsilyl- thymidyl-~2-(2,2-dimethyl-1,3-dioxolan-4-yl)ethyl1-morpho- linophosphoramidate (40) . Lithium diisopropylamide was prepared by adding butyllithium (2.1 ml, 4.20 mmol, 2.0M) to a stirred solution of diisopropylamine (0.58 ml, 4.20 mmol) in THF (1 ml) at 0°C. The mixture was allowed to stir at 0°C for 10 min. This solution was added dropwise to a stirred solution of i (680 mg, 1.91 mmol) in THF (6 ml) at 0°C. This alkoxide solution was then added dropwise to a stirred solution of 16d (600 mg, 1.91 mmol) in THF (5 ml) at 0°C, and stirring was continued overnight at room temperature. The solvent was then removed under reduced pressure and the residue purified by chromatography (EtOAc) to give 40. (835 mg, 69%): R f 0.73 (1:9 MeOH: CH 2 C1 2 ) .

Example 47. Preparation of 3'-0-t-Butyldimethylsilyl-2'- deoxy-5'-uridyl-T2-(2,2-dimethyl-l,3-dioxolan-4-yl)ethyl]- morpholinophosphoramidate (41) . Lithium diisopropylamide was prepared by adding butyllithium (1.93 ml, 3.85 mmol, 2.0M) to a stirred solution of diisopropylamine (0.54 ml, 3.85 mmol) in THF (1 ml) at 0°C. The mixture was allowed to stir at 0°C for 15 min. This solution was added drop-

wise to a stirred solution of 22. (6°0 ^g, 1.75 mmol) in TH (5 ml) at 0°C. This alkoxide solution was then added drop wise to a stirred solution of 16d (550 mg, 1.75 mmol) in THF (5 ml) at 0°C, and stirring was continued overnight at room temperature. The solvent was then removed under re¬ duced pressure and the residue purified by chromatography (EtOAc) to give 41 (556 mg, 51%): R f 0.70 (1:9 MeOH: CH 2 C1 ) .

Example 48. Preparation of 3 -O-t-Butyldimethylsilyl- thymidyl-f2-(4,4,β-trimethyltetrahydro-l,3-oxazin-2- yl)ethyllmorpholinophosphoramidate (42) . Compound 4_0 (835 mg, 1.32 mmol) was dissolved in 80% aqueous acetic acid in water (5 ml),, heated to 80°C for 30 min, cooled, and neu- tralized with NaOH. The solution was lyophilized, the residue taken up in THF, the salts removed by filtration, and the filtrate concentrated under reduced pressure to afford the diol (671 mg, 86%): R f = 0.56 (1:9 MeOH: CH 2 C1 2 ) ; 31 P NMR (CDC1 3 ) -15.53, -15.83 ppm (mixture of diastereo- mers). To a solution of the diol (671 mg, 1.13 mmol) in THF (4 ml) was added NaIO (242 mg, 1.13 mmol) in aqueous acetate buffer (5 ml, pH = 5.0, IM) . The mixture was allowed to stir for 7 min, and the THF was then removed under reduced pressure. The mixture was lyophilized, the residue taken up in THF, the salts filtered, and the fil¬ trate concentrated under reduced pressure. The residue was dissolved in CH 2 C1 2 (3 ml), and 4-amino-4-methyl-2-pentanol (132 mg, 1.13 mmol) in CH 2 C1 2 (3 ml) was added. The mix¬ ture was allowed to stir over 3 A sieves for 15 min. The sieves were removed and the solvent removed under reduced pressure. The residue was purified by chromatography (2% MeOH: EtOAc) to afford 4J2 (404 mg, 54%): R f 0.70.

Example 49. Preparation of 3 -O-t-Butyldimethylsilyl-2 - dioxy-5'-uridyl-r2-(4,4,β-trimethyltetrahydro-1,3-oxazin-2 yl)ethyl]-morpholinophosphora idate (43) . Compound 41 (54 mg, 0.88 mmol) was dissolved in 80% aqueous acetic acid " in water (3 ml), heated to 80°C for 30 min, cooled, and neu¬ tralized with NaOH. The solution was lyophilized, the residue taken up in THF, the salts removed by filtration, and the filtrate concentrated under reduced pressure to afford the diol (417 mg, 82%): R f = 0.55 (1:9 MeOH: CH 2 C1 2 ) ; 31 P NMR (CDC1 3 ) -15.10, -15.25 ppm (mixture of diastereo¬ mers). To a solution of the diol (417 mg, 0.72 mmol) in THF (3 ml) was added NaI0 A (154 mg, 0.72 mmol) in aqueous acetate buffer (3 ml, pH = 5.0, IM) . The mixture was al¬ lowed to stir for 7 min, and the THF was then removed unde reduced pressure. The mixture was lyophilized, the residu taken up in THF, the salts filtered, and the filtrate con¬ centrated under reduced pressure. The residue was dis¬ solved in CH 2 C1 2 (3 ml), and 4-amino-4-methyl-2-pentanol (84 mg, 0.72 mmol) in CH 2 C1 2 (3 ml) was added. The mixture was allowed to stir over 3 A sieves for 15 min. The sieves were removed and the solvent removed under reduced pres¬ sure. The residue was purified by chromatography (2% MeOH: EtOAc) to afford 4_3 (154 mg, 33%): R f 0.70.

Example 50. Preparation of Thymidyl- * 2-(4,4,6-trimethyl- tetrahγdro-l,3-oxazin-2-yl)ethyl]morpholinophosphoramidate

(3.) . Tetrabutylammonium fluoride (0.61 ml, 0.61 mmol, IM in THF) was added at 0°C to a stirred solution of 42 (404 mg, 0.61 mmol) in THF (3 ml). The mixture was allowed to stir for 20 min at 0°C. The solvent was removed under reduced pressure and the residue purified by chromatography (3% MeOH: EtOAc) to afford 3_ (66 mg, 20%): R f 0.69 (1:9 MeOH: CH 2 C1 2 ); • l E NMR (CDC1 3 ) 7.37(m, IH) , 6.25(m, IH) ,

4.51(m, IH), 4.38(m, IH) , 4.13(m, 5H) , 3.70(m, IH) , 3.65(m 4H), 3.15(m, 4H), 2.42(m, IH) , 2.17(m, IH) , 1.92(m, 5H) , 1.43(d, IH) , J = 13.08Hz), 1.13(m, 10H)ppm; 31 P NMR (CDC1 3 ) -15.69, -15.82, -16.02 ppm (mixture of diastereo- mers); IR (thin film) 3400, 2960, 1690, 1470, 1370, 1250, 1110, 975 cm "1 .

Example 51. Preparation of 2'-Deoxy-5'-uridyl-f2-(4,4,6- trimethyltetrahydro-l,3-oxazin-2-yl)ethyl]morphόlinophos- phoramidate (2) . Tetrabutylammonium fluoride (0.24 ml, 0.24 mmol, IM in THF) was added at 0°C to a stirred solu¬ tion of 4_3. (154 mg, 0.24 mmol) in THF (2 ml). The mixture was allowed to stir for 20 min at 0°C. The solvent was removed under reduced pressure and the residue purified by chromatography (3% MeOH: EtOAc) to afford 2 (62 mg, ' 49%): R f 0.69 (1:9 MeOH: CH 2 C1 2 ) ; X H NMR (CDC1 3 ) 7.60(m, IH) , 6.25(m, IH), 5.72(m, IH) , 4.51(m, IH) , 4.41(m, IH) , 4.15(m 5H) , 3.75(m, IH) , 3.67(m, 4H) , 3.13(m, 4H) , 2.45(m, IH) , 2.19(m, IH), 1.93(m, 2H) , 1.47(d, IH, J = 13.50Hz), 1.14(m 9H), 1.05(d, IH, J = 12.96Hz)ppm; 31 P NMR (CDC1 3 ) -15.89, -16.08 ppm (1:1 ratio of diastereomers); IR (thin film) 3420, 2960, 2920, 1690, 1460, 1350, 1260, 1110, 1090, 975, 910, 810, 730 cm "1 ; MS m/e 533(M + H) + , 555(M + Na) + .

Example 52. Preparation of Piperidinophosphoramidic di¬ chloride 44) . Triethylamine (18.25g, 180 mmol) was added, dropwise to a stirred solution of piperidine hydrochloride (lO.OOg, 82 mmol) and phosphorus oxychloride (12.63g, 82 mmol) in CH 2 C1 2 (100 ml) at 0°C. The mixture was allowed to stir overnight and then poured over ice. The layers were separated, and the aqueous layer was extracted with CH 2 C1 2 (3 x 100 ml). The organic layers were combined and dried (MgS0 ) . The filtrate was concentrated under reduced

pressure and the residue purified by chromatography (1:4 EtOAc: hexanes) to give 44. (13.92g, 84%): R f 0.70 (1:4 EtOAc: hexanes) .

Example 53. Preparation of 2- (2 ,2-dimethyl-l,3-dioxolan- 4-yl)-ethyl] piperidinophosphoramidate 45) . Butyllithium (11.00 ml, 22 mmol, 2.0M) was added dropwise at 0 β C to a stirred solution of 4-(2-hydroxyethyl)-2,2-dimethyl-l,3- dioxolane (2.92g, 20 mmol) and a crystal of 4-phenylazodi- phenylamine indicator in THF (7 ml). The resulting solu¬ tion was added dropwise at -78°C to a stirred solution of 44 (4.0g, 20 mmol) in.THF (5 ml). The mixture was allowed to stir at -78°C for 3 hr, at which time the purple solu¬ tion turned yellow. The mixture was warmed to room temper- ature and the solvent removed under reduced pressure. The residue was purified by chromatography (1:4 EtOAc: hexanes) to give 45. (2.69g, 43%): R f 0.65 (1:4 EtOAc: hexanes).

Example 54. Preparation of 3'-O-t-Butyldimethylsilyl-5- fluoro-2 * -deoxγ-5'-uridyl- \2-(2,2-dimethyl-l,3-dioxolan-4- yl)ethyl]-piperidinophosphoramidate (46) . Lithium diiso¬ propylamide was prepared by adding butyllithium (0.96 ml, 1.91 mmol, 2.0M) to a stirred solution of diisopropylamine (0.27 ml, 1.91 mmol) in THF (1.0 ml) at 0°C. The mixture was allowed to stir at 0°C for 15 min. This solution was added dropwise to a stirred solution of JL5. (313 mg, 0.87 mmol) in THF (6 ml) at 0°C. This alkoxide solution was then added dropwise to a stirred solution of 4_5_ (271 mg, 0.87 mmol) in THF (5 ml) at 0 °C, and stirring was con- tinued overnight at room temperature. The solvent was then removed under reduced pressure and the residue purified by chromatography (EtOAc) to give 4_6 (473 mg, 86%): R f 0.73 (1:9 MeOH: CH 2 C1 2 ) .

Example 55. Preparation of 3'-O-t-Butyldimethylsilyl-5- luoro-2'-deoxy-5'-uridyl-f2-( ,4,6-trimethyltetrahydro- l,3-oxazin-2-yl)ethyl]-piperidinophosphoramidate (47) . Compound 46 (473 mg, 0.74 mmol) was dissolved in 80% aqueous acetic acid in water (5 ml), heated to 80°C for 30 min, cooled, and neutralized with NaOH. The solution was lyophilized, the residue taken up in THF, the salts removed by filtration, and the filtrate concentrated under reduced pressure to afford the diol (368 mg, 83%): R f = 0.56 (1:9

MeOH: CH 2 C1 2 ); 31 P NMR (CDC1 3 ) -14.19, -14.54, -14.65, -14.74 ppm (mixture of diastereomers). To a solution of the diol (368 mg, 0.62 mmol) in THF (4 ml) was added NaI0 (132 mg, 0.62 mmol) in aqueous acetate buffer (4 ml, pH = 5.0, IM) . The mixture was allowed to stir for 10 min, and the THF was then removed under reduced pressure. The mixture was lyo¬ philized, the residue taken up in THF, the salts filtered, and the filtrate concentrated under reduced pressure. The residue was dissolved in CH 2 C1 2 (3 ml), and 4-amino-4- methyl-2-pentanol (84 mg, 0.72 mmol) in CH 2 C1 2 (3 ml) was added. The mixture was allowed to stir over 3A sieves for 15 min. The sieves were removed and the solvent removed under reduced pressure. The residue was purified by chrom¬ atography (2% MeOH: EtOAc) to afford 4_7 (67 mg, 17%): R f 0.70.

Example 56. Preparation of 5-Fluoro-2'-deoxy-5'-uridyl-f2- (4,4,6-trimethyltetrahydro-l,3-oxazin-2-yl)ethyl] iper¬ idinophosphoramidate ( .) . Tetrabutylammonium fluoride (0.104 ml, 0.10 mmol, IM in THF) was added at 0°C to a stirred solution of 47 (67 mg, 0.10 mmol) in THF (2 ml). The mixture was allowed to stir for 20 min at 0°C. The solvent was removed under reduced pressure and the residue

purified by chromatography (3% MeOH: EtOAc) to afford 4. (10 mg, 18%): R f 0.70 (1:9 MeOH: CH 2 C1 2 ); l E NMR (CDC1 3 ) 7.75(m, IH), 6.21(m, IH), 4.52(m, IH), 4.42(m, IH), 4.12(m, 5H), 3.71(m, IH), 3.09(m, 4H) , 2.42(m, IH) , 2.19(m, IH) , 1.91(m, 2H), 1.52(m, 6H) , 1.41(d, IH, J = 12.96Hz), 1.13(m,

10H)ppm; 31 P NMR (CDCL 3 ) -14.13, -14.36 ppm (1:1 ratio of diastereomers) .

Example 57. Biological Activity. A. Cytotoxicity against B16 Melanoma Cells. B16 cells in exponential growth (2-3 x 10 6 cells in 10 ml of serum-free MEM medium) were treated with drug for 2 hr. The cells were separated, washed, and resuspended in MEM medium supplemented with 10% fetal bovine serum. The cells were plated in 60-mm culture dishes at a density of 50- 50,000 cells/plate (depending upon the drug concentration used initially) and then incubated for 8 days in a C0 2 incubator at 37°C. The colonies were fixed and stained with 0.5% crystal violet in ethanol and counted. The results are summarized in Table I above.

B. Cyctotoxicity Against L1210 Leukemia Cells. In addition to the B16 melanoma cell assay sum¬ marized in Table I, compounds la-e, 5. and 7. were evaluated for growth inhibitory activity against L1210 leukemia cells. Stock solutions of the compounds were prepared in 95% ethanol, and serial dilutions of drug were prepared in ethanol such that 50 μl of drug solution added to 10 ml of cell suspension gave the desired final concentration. L1210 cells in exponential growth were suspended in Fischer's medium supplemented with 10% horse serum, 1% glutamine, and 1% antibiotic-antimycotic solution to give

10-ml volumes of cell suspension at a final density of

3-6 x 10 4 /ml. Appropriate volumes of the solutions of each

compound were transferred to the cell suspensions, and incubation was continued for 2, 8, 24, or 48 hr. The cell were spun down, resuspended in fresh drug-free medium, and returned to the incubator, then counted with a Coulter Counter 48 hr after treatment with the compound. The results are summarized on Table III, below.

Data represents an average of at least two experiments; L1210 cells were treated with compound for 2, 8, 24 and 48 hr. The drug-containing medium was removed, cells were washed, complete medium was added, and the cells were incubated for 48 hr total. Cell counts were ob¬ tained 48 hr after the start of treatment.

The bromo compound .la was a potent inhibitor of cell proliferation using a 2 hr contact time. The inhibi¬ tory activity was completely blocked by addition of 5 μM thymidine, confirming that this compound was acting via inhibition of thymidylate synthetase. The potency of la.

increased with longer treatment times and was 1-2 orders magnitude more potent than 5-FU using treatment times of 8, 24, and 48 hr. Comparable inhibition was observed wit the iodo and tosyl analogs. The chloro analog lc. r whose phosphoramidate would be expected to have a slower rate o alkylation, was less potent than La . , JLb, and Id at shorte exposure times but equipotent in the 24- and 48-hour treat ment groups. The relationship between potency and alky- lating activity was confirmed by the synthesis and evalu- ation of the non-alkylating orpholino phosphoramidate le. It is interesting to note that le is comparable in potency to 5-FU at long treatment times; the activity of a_ is als completely reversed by addition of thymidine, suggesting that thymidylate synthetase also represents the target for this compound. Thus, le might be a prodrug for FdUMP; the intracellular cleavage of the morpholine substituent is presumably enzymatic, because the morpholinophosphoramidat derivative NucOP(O) (NR 2 R 3 ) (0") is stable to hydrolysis unde physiologic conditions.

All patents, patent documents and publications cited herein are incorporated by reference herein. The invention has been described with reference to various specific and preferred embodiments and techniques. - How¬ ever, it should be understood that many variations and modifications may be made while remaining within the spiri and scope of the invention.