B&P FILE NO. 15358-3

TITLE: METHOD FOR PREPARING 2-IODO TRITERPENOID COMPOUNDS FIELD OF THE INVENTION

The present invention relates to methods for the preparation of 2-iodo triterpenoid compounds, and the use of these compounds as versatile intermediates for the preparation of 2-substituted triterpenoid compounds. BACKGROUND OF THE INVENTION

The terpenoids, sometimes referred to as isoprenoids, are a large and diverse class of naturally occurring organic chemicals, derived from five- carbon isoprene units assembled and modified in thousands of ways. Most are multicyclic structures which differ from one another not only in functional groups, but also in their basic carbon skeletons. These lipids can be found in all classes of living things, and are one of the largest group of natural products. Triterpenes consist of six isoprene units. The linear triterpene squalene, the major constituent of shark liver oil, is derived from the reductive coupling of two molecules of farnesyl pyrophosphate. Squalene is then processed biosynthetically to generate either lanosterol or cycloartenol, the structural precursors to all the steroids.

The chemical modification of triterpenoids, including steroids, has been well investigated over the years. Certain modifications remain a challenge and optimizations and new methods for the functionalization of the triterpenoid skeleton are always dersirable. SUMMARY OF THE INVENTION

In the present disclosure a simple method for the preparation of 2-iodo- 3-oxo-triterpenoid compounds from the corresponding 1-ene-3-one compounds has been developed. The 2-iodo-3-oxo-triterpenoid compounds are versatile intermediates in the preparation of 2-substituted-3-oxo triterpenoids using well known methods for the conversion of vinyl iodo compounds, for example in metal-catalyzed reactions. Accordingly, the present invention includes a method for preparing compounds of Formula I:

wherein R ¹ , R ² and R ³ are independently selected from H and C-^alkyl and —~v represents any triterpenoid skeleton, comprising contacting a compound of the Formula II:

wherein R ¹ , R ² and R ³ are independently selected from H and and • _" ~ _™ represents any triterpenoid skeleton, with iodine and pyridine in an ether solvent under conditions for the formation of the compound of Formula I and optionally isolating and purifying the compound of Formula I.

The method of the invention produces the desirable products of the Formula I, which are useful intermediates in the preparation of other 2- functionalized triterpenoid compounds. Accordingly, the present invention also includes a method of preparing compounds of Formula III:

wherein R ¹ , R ² and R ³ are independently selected from H and Ci- ₄ alkyl; •~«~ _" represents any triterpenoid skeleton; and

R ⁴ is any group that is incorporated into the compounds of Formula I by a metal-catalyzed reaction, comprising reacting a compound of the Formula I prepared using a method as described above under metal-catalyzed reaction conditions. The present invention also includes a compound of the Formula I selected from:

2-lodo-5α-cholest-1-ene-3-one (Ib); Methyl-2-iodo-3-ketoursa-1 ,12-diene-28-oate (Ic); Methyl 3,12-diketo-2-iodo-cholan-1-ene-24-oate (Id); and Diketoursa-1 ,12-diene-2-iodo-28-oate (If), and salts, including pharmaceutically acceptable salts, thereof.

Other features and advantages of the present invention will become apparent from the following detailed description. It should be understood, however, that the detailed description and the specific examples while indicating preferred embodiments of the invention are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. DETAILED DESCRIPTION OF THE INVENTION In a study of the activity of 2-substituted 3-oxo-glycyrrhetinic acid derivatives, the present inventors sought to prepare the corresponding 2-iodo compound as an intermediate to be used to access a variety of these desired compounds. A recently reported method (Kraft, ME and Cran JW, Synlett, 2005, 1263-1266) for the α-iodination of α,β-unsaturated carbonyl compounds did not work well in this instance. However, a modification of some earlier procedures (Kobayashi, S. et al. J. Org. Chem. 2006, 71 :636-644) unexpectedly allowed the development of a satisfactory preparation of 2-iodo- 3-oxo-triterpenoid derivatives from the corresponding 3-ol or 3-one via the 1- ene-3-one. Accordingly, the present invention includes a method for preparing compounds of Formula I:

wherein R ¹ , R ² and R ³ are independently selected from H and d^alkyl, suitably H or methyl) and -~*~~ represents any triterpenoid scaffold, comprising contacting a compound of the Formula II:

wherein R ¹ , R ² and R ³ are independently selected from H and Ci _-4 alkyl and -~— represents any triterpenoid skeleton, with iodine and pyridine in an ether solvent under conditions for the formation of the compound of Formula I and optionally isolating and purifying the compound of Formula I.

By "triterpenoid skeleton" it is meant any triterpenoid-like ring system containing a minimum of 4 fused rings, such as the 6,6,6,5 fused-ring skeleton of a steroid:

and up to 5 fused rings, such as the 6,6,6,6,6 fused-ring skeleton of pentacyclic triterpenoids:

including any functionalizations, ring expansions and ring contractions thereof.

A list of non-limiting examples of common steroids is found in Table 1. Non- limiting examples of pentacyclic triterpenoids include, glycyrretinic acid, oleanolic acid, ursolic and betulinic acids and derivatives thereof. As used herein, the term "derivatives thereof refers to any functionalization, ring expansion and/or ring contraction of the triterpenoid or triterpenoid-like skeleton. Such modifications of triterpenoid skeletons is well known in the art, for example as described in Moss, GP. Pure and Appl. Chem. Vol. 61 , No.

10, pp. 1783-1822, 1989. In specific embodiments of the invention, the compound of formula Il is a compound selected from:

5α-Cholest-1-ene-3-one (Ha);

Methyl 3,12-diketocholan-1-ene-24-oate (lie); Methyl 3,11-diketoursa-1,12-diene-28-oate (lie);

Methyl 3-ketoursa-1 ,12-diene-28-oate (lit); and

Methyl 3,11-dioxo-18β-oleana-1,12-diene-30-oate (Hh).

In further embodiments of the invention the compound of Formula I is selected from: Methyl 2-iodo-3,11-dioxo-18β-oleana-1 ,12-diene-30-oate (Ia);

2-lodo-5α-cholest-1-ene-3-one (Ib);

Methyl 2-iodo-3-ketoursa-1 ,12-diene-28-oate (Ic);

Methyl 3,12-diketo-2-iodo-cholan-1-ene-24-oate (Id); and

Diketo-ursa-1 , 12-diene-2-iodo-28-oate (If), In embodiments of the present invention the expression "under conditions for the formation of the compound of Formula I" refers to reaction of the compounds of Formula I in the presence of iodine and pyridine at a molar ratio of about 1 :2:3 to about 1 :2:5 in an ether solvent. In a further embodiment of the invention the ether solvent is tetrahydrofuran. Suitably,

the concentration of the compound of Formula Il in the ether solvent is about 0.001 M to about 1 M, more suitably about 0.01 M to about 0.5M, even more suitably about 0.1 M. The reaction is suitably performed at a temperature of about 20 ⁰ C to about 100 ⁰ C, more suitably about 40 ⁰ C to about 90 ⁰ C. even more suitably about 80 ⁰ C. The compounds of Formula I may optionally be isolated and purified using methods known in the art, for example, by extraction, washing with various salt solutions and/or water, removal of water, removal of solvent, recrystallization and/or chromatography.

The compounds of Formula Il are either known in the art or may be prepared using methods known in the art. For example, the corresponding 3 oxo or 3-hydroxy compounds may be reacted with 2-iodoxybenzoic acid (IBX) as per a reported method (K.C. Nicolaou, T. Montagnon, P. S. Baran and Y.-L. Zhong, J. Am. Chem. Soc, 2002, 124, 2245-2258) to provide compounds of Formula II. The compounds of Formula I are versatile intermediates in the preparation of 2-substituted triterpenoid compounds. The vinyl iodo group readily undergoes metal-catalyzed transmetallation reactions, for example as described in the following non-limiting publications: Negishi, E. J. Organomet. Chem. pp. 179, 1999; Zhang, X. et al. J. Fluorine Chem. 2001 , 108, 79-82; Ostwald, R. et al. J. Org. Chem. 1994, 59, 4143-4153; Johnson, CR. et al. Tetrahedron Lett. 1992, 33, 919-922; Fei, X.-S. et al. J. Chem. Soc. Perkin Trans. I. 1998, 1139-1142; and Yamakawa, I. et al. Tetrahedorn Lett. 1991 , 32, 2045-2048. Accordingly, the present invention also includes a method of preparing 2-substituted triterpenoid compounds of Formula III:

wherein R ¹ , R ² and R ³ are independently selected from H and Ci _-4 alkyl; ~~~v represents any triterpenoid skeleton; and

R ⁴ is any group that is incorporated into the compounds of Formula I by a transition metal-catalyzed reaction, comprising reacting a compound of the Formula I prepared using a method as described above under metal-catalyzed reaction conditions. Suitably the reaction conditions are metal-catalyzed transmetalation reaction conditions.

In embodiments of the invention, R ⁴ is selected from C _h alky!, C _2- βalkenyl, C ₂ - ₆ alkenyl, heteroaryi, aryl, fluorosubstituted C-i-βalkyl, CN, halo.

Unless specified otherwise, the term "alkyl", when used alone or in combination with other groups or atoms, refers to a saturated straight or branched chain consisting solely of 1 to 6 hydrogen-substituted carbon atoms, suitably 1 to 4 hydrogen-substituted carbon atoms, and includes methyl, ethyl, propyl, isopropyl, n-butyl, s-butyl, isobutyl, t-butyl, 2,2-dimethylbutyl, n-pentyl, 2-methylpentyl, 3-methylpentyl, 4-methylpentyl, n-hexyl and the like.

Unless specified otherwise, the term "alkenyl" refers to a partially unsaturated straight or branched chain consisting solely of 2 to 6 hydrogen- substituted carbon atoms that contains at least one double bond, and includes vinyl, allyl, 2-methylprop-1-enyl, but-1-enyl, but-2-enyl, but-3-enyl, 2- methylbut-1-enyl, 2-methylpent-1-enyl, 4-methylpent-1-enyl, 4-methylpent-2- enyl, 2-methylpent-2-enyl, 4-methylpenta-1 ,3-dienyl, hexen-1-yl and the like. Unless specified otherwise, the term "alkynyl" refers to a partially unsaturated straight or branched chain consisting solely of 2 to 8 hydrogen- substituted carbon atoms that contains at least one triple bond, and includes ethynyl, 1-propynyl, 2-propynyl, 2-methylprop-1-ynyl, 1-butynyl, 2-butynyl, 3- butynyl, 1 ,3-butadiynyl, 3-methylbut-1-ynyl, 4-methylbut-ynyl, 4-methylbut-2- ynyl, 2-methylbut-1-ynyl, 1-pentynyl, 2-pentynyl, 3-pentynyl, 4-pentynyl, 1 ,3- pentadiynyl, 1 ,4-pentadiynyl, 3-methylpent-1-ynyl, 4-methylpent-2-ynyl, 4- methylpent-2-ynyl, 1-hexynyl and the like.

Unless specified otherwise, the term "fluoro-substituted" as used herein means that, in the group being described, one or more, including all, of the hydrogen atoms has been replaced by F. For example, a fluoro-substituted alkyl includes trifluoromethyl, trifluoroethyl, pentafluoroethyl and the like.

Unless specified otherwise, as used herein, the terms "halogen" and "halo" include F, Cl, Br, and I.

Unless specified otherwise, as used herein, the term aryl refers to an aromatic mono- or bicyclic group containing from 6 to 14 carbon atoms that may be optionally fused with a fully or partially saturated carbocyclic ring and may optionally be substituted with one or more substituents, suitably one to three substituents, independently selected from d^alkyl, fluoro-substituted Ci.4alkyl, halo, OCi _-4 alkyl, fluoro-substituted OC _1-4 alkyl, NO ₂ and CN. Examples of aryl groups include phenyl, naphthyl, indanyl and the like. Unless specified otherwise, as used herein, the term heteroaryl refers to an aromatic mono- or bicyclic group containing from 5 to 14 carbon atoms, of which one to five is replaced with a heteroatom selected from N, S and O, that may optionally be substituted with one or more substituents, suitably one to three substituents, independently selected from Ci^alkyl, fluoro-substituted C _1-4 alkyl, halo, OC _1-4 alkyl, fluoro-substituted OC _1-4 alkyl, NO ₂ and CN. Examples of aryl groups include thienyl. benzimidazolyl, benzo[b]thienyl, furyl, benzofuranyl, pyranyl, isobenzofuranyl, chromenyl, xanthenyl, pyrrolyl, imidazolyl, pyrazolyl, pyridyl, pyrazinyl, pyrimidinyl, pyridazinyl, indolizinyl, isoindolyl, indolyl, indazolyl, purinyl, quinolizinyl, isoquinolyl, quinolyl, and the like.

Suitably, the important trifluoromethyl group (R ⁴ = CF ₃ ) may be incorporated at the 2-position by reaction of the compounds of Formula I with methyl fluorosulfonyldifluoroacetate in the presence of copper iodide and hexamethylphosphoramide, for example as described in Zhang, X. et al. J. Fluorine Chemistry, vol. 108, pp. 79-82, 2001.

As the compounds of Formula I are new, and are useful as intermediates in the preparation of biologically active triterpenoid compounds and/or are themselves, biologically active triterpenoid compounds, the present invention also includes a compound of the Formula I selected from: 2-lodo-5α-cholest-1-ene-3-one (Ib);

Methyl 2-iodo-3-ketoursa-1 ,12-diene-28-oate (Ic); and Methyl 3,12-diketo-2-iodo-cholan-1-ene-24-oate (Id);

Diketo-ursa-1 , 12-diene-2-iodo-28-oate (If), and salts, including pharmaceutically acceptable salts, thereof.

The term "pharmaceutically acceptable" as used herein means compatible with the treatment of animals, including humans. In understanding the scope of the present disclosure, the term

"comprising" and its derivatives, as used herein, are intended to be open ended terms that specify the presence of the stated features, elements, components, groups, integers, and/or steps, but do not exclude the presence of other unstated features, elements, components, groups, integers and/or steps. The foregoing also applies to words having similar meanings such as the terms, "including", "having" and their derivatives. Finally, terms of degree such as "substantially", "about" and "approximately" as used herein mean a reasonable amount of deviation of the modified term such that the end result is not significantly changed. These terms of degree should be construed as including a deviation of at least ±5% of the modified term if this deviation would not negate the meaning of the word it modifies.

Unless otherwise indicated, the terms "a", "an" and "the" as used herein mean one or more that one. EXAMPLES MA TERIALS AND METHODS

Melting points were determined with a Kofler hot-stage apparatus. ¹ H NMR spectra were run in CDCb on a Bruker Avance-400 spectrometer using Mβ4Si as an internal standard. For analytical and preparative use, TLC plates were spread with Silica Gel 60 GF (Merck). Silica for column chromatography was obtained from Selecto Scientific. Elemental microanalyses were carried out by Guelph Chemical Laboratories Ltd. All starting materials and reagents were purchased from Sigma-Aldrich.

Example 1: Reaction of 5α-cholestan-3-one (IVa) with IBX to give cholesta- 1 ,4-diene-3-one (lib) and 5α-cholesta-1-ene-3-one (Ha)

A mixture of 5α-cholestan-3-one (IVa, 193.3 mg, 0.500 mmol) and iodoxybenzoic acid (168 mg, 0.600 mmol, 1.2 eq.) in dimethyl sulfoxide (8 ml_, freshly distilled from CaH ₂ ) was stirred with heating at 80 - 85° C for 24 h.

After cooling, the solution was poured into water (80 mL) and 5% aqueous

NaHCθ ₃ (40 mL) to give a cloudy precipitate. The mixture was extracted with diethyl ether (3 x 50 mL) and the combined extracts were dried over anhydrous Na ₂ SO ₄ . Evaporation of the ether extracts gave a yellow-amber solid residue (191.7 mg) which showed three UV active bands on preparative

TLC (MeOH/CH ₂ CI ₂ ; 1 :99).

5o-Cholesta-1-ene-3-one (Ha)

The least polar band gave the compound Ha as white crystals (120.7 mg, 62.8%). ¹ H δ 7.146 (1 H, d, J = 10.2 Hz, C1-H), 5.850 (1 H, d, J = 10.2 Hz, C2-H), 1.006 (3H, s), 0.914 (3H, d, J = 6.5 Hz), 0.874 (3H, d, J = 1.7 Hz), 0.857 (3H, d, J = 1.7 Hz). Cholesta-1 ,4-diene-3-one (lib)

The most polar band gave compound Mb as faintly amber crystals (6.1 mg, 3.2%). ¹ H NMR δ 7.176 (1 H, d, J = 10.2 Hz, C1-H), 6.238 (1 H, dd, J = 10.2 and 1.7 Hz, C2-H), 6.068 (1H, C4-H), 1.227 (3H, s), 0.903 (3H ₁ d, J = 6.5 Hz), 0.870 (3H, d, J = 1.8 Hz), 0.853 (3H, d, J = 1.8 Hz), 0.735 (3H, s).

Example 2: Reaction of methyl deoxycholate (IVb) with IBX to give methyl 3, 12-diketo-chola-i-eneoate (lie), methyl 3, 12-diketo-chola-1 ,4-dieneoate (Hd) and methyl 3, 12-diketo-chola-3-eneoate (V)

(V)

Methyl deoxycholate was prepared by diazomethylation of the carboxylic acid and a sample (235.2 mg, 0.578 mmol) was reacted with the IBX reagent (810.0 mg, 2.892 mmol, 5 eq.) at 60 - 65° C as described in Example 1. After a similar work-up, evaporation of the combined extracts gave a colorless gum which solidified on standing (235.2 mg). Preparative TLC (MeOH/CH ₂ CI ₂ ; 1 :49) showed four UV active bands. Methyl 3, 12-diketo-chola-1 -eneoate (lie)

The least polar band gave a mixture of the titled compound Mc and IV as a faintly amber solid (66.3 mg, 28.6 %). The former shows ¹ H NMR δ 6.658 (1 H, d, J = 10.2 Hz, C1-H), 5.929 (1H, d, J = 10.2, C2-H) and two sets

of resonances in the methyl region, 1.274 (s), 1.066 (s) and 0.849 (d, J = 6.5

Hz) and 1.113 (s), 1.058 (s) and 0.861 (d, J = 6.5 Hz) in a ratio of ~ 10:9 respectively.

Methyl 3, 12-diketo-chola-i ,4-dieneoate (Hd)

The second most polar band gave the titled compound Md as a faintly amber solid (8.0 mg, 3.5 %). ¹ H NMR δ 6.876 (1H, d, J = 9.4 Hz, C1-H), 6.252 (1H, dd, J = 9.4 and 1.8 Hz, C2-H), 6.097 (1H, apparent t, J = 1.4 Hz, C4-H), 1.318 (3H, s), 1.113 (3H, s), 0.872 (3H, d). Methyl 3, 12-diketo-chola-3-eneoate (V)

The middle major band gave the titled compound V as a white solid (118.4 mg, 51.1 %). ¹ H NMR δ 5.767 (1H, br d, J = 1.6 Hz, C4-H), 1.275 (3H, s), 1.092 (3H, s), 0.864 (3H, d, J = 6.5 Hz).

Example 3: Reaction of methylursolate (IVc) with IBX reagent to give methyl 3, 11-diketoυrsa-1, 12-diene-28-oate (He) and methyl 3-ketoursa-1,12-diene- 28-oate (Hf)

(IVc) (lie)

(Hf)

Methyl ursolate (IVc) was prepared by diazomethylation of ursolic acid and a sample (522.7 mg, 1.120 mmol) was reacted with IBX reagent (941.0 mg, 3.360 mmol, 3 eq.) as described in Example 1. After a similar work-up, evaporation of the combined extracts gave a yellow gum (585.2 mg) which showed three prominent UV bands on preparative TLC (MeOH/Ch^Cb; 1 :49). Methyl 3, 11-Diketoursa-i, 12-diene-28-oate (lie)

The second most polar band gave the titled compound (lie) as a faintly amber gum (82.2 mg). ¹ H δ 7.749 (1H, d, J = 10.2 Hz, C1-H), 5.809 (1H, d, J = 10.2 Hz ₁ C2-H), 5.702 (1 H, s), 3.628 (3H, s) 1.402 (3H, s), 1.327 (3H, s), 1.153 (3H, s), 1.105 (3H, s), 0.978 (3H, d, J = 6.4 Hz), 0.963 (3H, s), 0.883 (3H, d, J = 2.5 Hz). Methyl 3-ketoursa-1 , 12-diene-28-oate (Hf)

The least polar band gave the titled compound Hf as a white foamy solid (322.1 mg). ¹ H δ 7.062 (1 H, d, J = 10.1 Hz, C1-H), 5.809 (1 H, d, J = 10.1 Hz, C2-H), 5.323 (1H, t, J = 3.6 Hz, C12-H), 3.621 (3H, s) 1.159 (3H, d, J = 7.4 Hz), 1.097 (6H, s), 0.947 (3H, d, 6.2 Hz), 0.870 (3H, d, J = 6.4 Hz), 0.842 (3H, s).

Example 4: lodination of methyl 3, 11-dioxo-18β-oleana-1 , 12-diene-30-oate (Hh) to give methyl 2-iodo-3, 11-dioxo-18β-oleana-1, 12-diene-30-oate (Ia)

(iih) (Ia)

A mixture of methyl 3,11-dioxo-18β ^~ -oleana-1 ,12-diene-30-oate (prepared as described in Chintharlapalli, S. et al. MoI. Cane. Ther. vol. 6, pp. 1-11 , 2007) (Hh, 437.6 mg, 0.9104 mmol), iodine (462.2 mg, 1.821 mmol) and

pyridine (216 mg, 2.73 mmol) in tetrahydrofuran (10 ml_) was stirred and heated at reflux for 5 h. The solvent was then removed in vacuo and the resulting dark gum dissolved in CH ₂ CI ₂ (25 ml_). This solution was washed, successively, with aqueous sodium hydroxide (2 g in 20 mL), water (10 mL), hydrochloric acid (7.5 mL cone. HCI, 12.5 mL water), water (10 mL) and brine (20 mL). The solution was then dried over sodium sulfate. An analytical TLC of this solution (MeOH/CH ₂ CI ₂ , 1 :49) showed one major spot and a minor, more polar, spot corresponding to substrate. The solution was evaporated in vacuo to give an amber residue (607.7 mg) which was dissolved in CH ₂ CI ₂ and subjected to column chromatography (SiO ₂ , 32-63 mm, 20 g). Traces of residual iodine were washed off with CH ₂ CI ₂ and the product (534.0 mg) was recovered by washing with MeOHZCH ₂ CI ₂ (3:47). Crystallization of this white solid from hexane afforded colorless needles (512.9 mg, 92.9%) of the title compound. ¹ H NMR δ 8.538 (1H, s, C1-H), 5.782 (1H, s, C12-H), 3.711 (3H, s, OMe) ₁ 2.722 (1 H, s, C9-H), 1.454, 1.429, 1.400, 1.249, 1.167, 0.828 (all 3H, s. CMe), 1.172 (6H ₁ S ₁ 2 x CMe).

Example 5: lodination of 5α-cholest-1-ene-3-one (Ha) to give 2-/odo-5α- cholest-1-ene-3-one (Ib)

^(lla) (Ib)

A mixture of 5α-cholest-1-ene-3-one (Ha, Example 1) (191.3 mg, 0.497 mmol), iodine (265.4 mg, 1.046 mmol), and pyridine (195 mg, 2.5 mmol) in tetrahydrofuran (5 mL) was stirred at room temperature for 48 hours, the solvent was removed in vacuo and the dark residue was transferred with CH ₂ CI ₂ (2- 3 mL) to a separatory funnel. Diethyl ether (25 mL) was added and the solution was successively washed with aqueous sodium hydroxide (2g in 10 mL), water (10 mL), hydrochloric acid (2 mL cone. HCI, 10 mL water)

and water (10 ml_). The organic layer was dried over anhydrous Na ₂ SO ₄ and then concentrated in vacuo to give a white solid (260.4 mg). Preparative TLC (MeOH/CH ₂ CI ₂ ; 1/149) showed one major UV active band. The title compound was isolated as a white solid (234.9 mg, 93%). ¹ H δ 7.908 (1 H,s, C1-H), 2.520 (2H, main J = 17 - 18 Hz), 1.032 (s, 3H), 0.910 (3H, d, J = 6.6 Hz), 0.869 (3H, d, J = 6.6 Hz), 0.864 (3H, d, J = 6.6 Hz), 0.689 (3H, s). Example 6: lodination of methyl 3-ketoursa-1 , 12-diene-28-oate (Hf) to give methyl 2-iodo-3-ketoursa-1 , 12-diene-28-oate (Ic)

(iif) (Ic)

A mixture of methyl-3-ketoursa-1 ,12-diene-28-oate (Hf, Example 3) (322.1 mg, 0.690 mmol), iodine (350.3 mg, 1.380 mmol), and pyridine (245 mg, 3.1 mmol) in tetrahydrofuran (8 ml_) was stirred and heated at 70 - 75 ⁰ C for 24 h. Since analytical TLC (MeOH/CH ₂ CI ₂ , 1:99) revealed that the reaction was incomplete, stirring and heating was continued for additional 48 h. Analytical TLC again revealed that the reaction was incomplete and therefore fresh iodine (280.6 mg, 1.106 mmol) was added and the reaction mixture was stirred and heated for another 24 h. The solvent was removed in vacuo and the dark residue was transferred with CH ₂ CI ₂ (4 mL) to a separatory funnel containing diethyl ether (25 mL). This solution was successively washed with aqueous sodium hydroxide (2g in 10 mL), water (10 mL), hydrochloric acid (2 mL cone. HCI, 10 mL water) and water (10 mL). The organic layer was dried over anhydrous Na ₂ SO ₄ and then the solvent was concentrated in vacuo to give a light amber gum (469.5 mg). Preparative TLC (MeOH/CH ₂ CI ₂ ; 1 :149) showed two major UV active bands and a faint band of

intermediate polarity. The least polar band gave the titled compound as a faintly yellow amber gum (324.1 mg, 79%). ¹ H δ 7.822 (1H, s, C1-H), 5.322 (1 H, approx. t, J = 3.6 Hz, C12-H), 1.186 (6H ₁ s), 1.157 (3H, s), 1.111 (3H, s), 0.826 (3H, s), 0.953 (3H, d, J = 6.1 Hz), 0.882 (3H, d, 6.4 Hz). Example 7: lodination of methyl 3, 12-diketo-cholan-1-ene-24-oate (lie) to give methyl 3, 12-diketo-2-iodo-cholan-1-ene-24-oate (Id)

Using the method described in Examples 5-6, the titled compound was prepared from methyl 3,12-diketo-cholan-1-ene-24-oate (lie, Example 2). ¹ H δ 7.451 (1 H, s, C1-H), 3.666 (3H, s), 1.292 (3H, s), 1.062 (3H ₁ s), 0.851 (3H, d, J = 6.4). Example 8: lodonation of diketo-ursa-1 , 12-diene-28-oate (He) to give diketo- ursa- 1 , 12-diene-2-iodo-28-oate (If)

(lie) (If)

Using the method described in Examples 5-6, the titled compound is prepared from diketo-ursa-1,12-diene-28-oate (lie, Example 3).

Example 9: Preparation of methyl 3, 11-dioxo-2-trifluoromethyl-18β-oleanana- 1,2-diene-30-oate (Ilia)

(Ia) (Ilia) Dimethyl formamide (ca 15 ml_; dried by stirring over CaH ₂ overnight under N ₂ ) was vacuum-transferred into a dry Schlenk tube containing methyl 3,11-dioxo-2-iodo-18β-oleanana-1 ,2-dien-30-oate (Ia, Example 5) (216.8 mg, 0.3574 mmol) and cuprous iodide (166.6 mg, 0.8744 mmol). This mixture was allowed to warm up to ambient temperature under vacuum and then N ₂ was admitted. The resulting solution, containing some suspended solid, was heated to 7O ⁰ C with stirring under N ₂ , and methyl fluorosulfonyldifluoroacetate (0.66 ml_, 1.0 g, 5.2 mmol) and then hexamethylphosphoramide (1.0 ml_) were added by syringe. Stirring of the resulting somewhat cloudy solution, was continued, with heating, under N ₂ for 20 h. The reaction solution containing a fine suspension of a rust-coloured solid, was allowed to cool and then a saturated aqueous ammonium chloride solution (30 mL) was added. The resulting solution was extracted with diethyl ether three times (30, 15, and 15 mL); the rust-coloured solid adhered to the walls of the separating funnel. The combined ether extracts were dried over anhydrous sodium sulphate.

Evaporation of the dried extracts in vacuo left a colourless oily solid which was subjected to preparative TLC (Merck silica, eluant MeOH/CH ₂ CI ₂ , 1:99). The resulting plates showed one major band along with a minor very polar one. The main band was recovered and eluted with MeOH/CH ₂ CI ₂ (1:19). Evaporation of the solvent in vacuo left a colorless, crystalline solid

(172.0 mg) which was crystallized from hexane to give clear stout needles (150.4 mg) of methyl 3,11-dioxo-2-trifluoromethyl-18β-oleanana-1 ,2-diene-30- oate (Ilia): mp 221-223 ⁰ C (with sublimation from 208 ⁰ C). ¹ H NMR spectrum, δ 8.212(1H, s, C-1H), 5.809 (1H ₁ s, C-12H), 3.709 (3H, s, OMe), 2.721 (1H, s, C-9H), 1.429, 1.410, 1.199, 1.184, 1.171 , 1.164 and 0.837 (all 3H, s, CMe).

While the present invention has been described with reference to what are presently considered to be the preferred examples, it is to be understood that the invention is not limited to the disclosed examples. To the contrary, the invention is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

All publications, patents and patent applications are herein incorporated by reference in their entirety to the same extent as if each individual publication, patent or patent application was specifically and individually indicated to be incorporated by reference in its entirety. Where a term in the present application is found to be defined differently in a document incorporated herein by reference, the definition provided herein is to serve as the definition for the term.

Table 1