The present invention relates to a new diterpene with taxane nucleus having an itumor activity. From spectrometric analysis, the new compound was given the structural formula (1), corresponding to the ester at the 13-position of 5β,20-epoxγ-l,2α,4,7β,10β,13α-hexa- hydroxytax-ll-en-9-one 4,10-diacetate 2-benzoate with (2R,3S)-N-hexanoyl-3-phenylisoserine.

The compound of formula (1) has been isolated from the root bark of the Taxus genus, with yields ranging from 0.02 to 0.06%. The vegetal material, which the compound (1) is extracted from, preferably consists of the roots of yew cultivar, for example the bark of Taxus media cv Hick- sii. This cultivar is currently used with ornamental purposes for garden dressing. This fact allows to avoid the indiscriminate harvesting of the roots of spontane¬ ous yew trees, whose growth is notoriously slow, and their consequent rapid extinction.

The compound (1) is extracted by means of chlori¬ nated solvents, for example dichloromethane, pure or in

admixture with alcohols, for example methyl and ethyl alcohol. The extraction of the vegetal material can be carried out also by using ketones, for example acetone, pure or in admixture with water. The root bark extract contains, in addition to compound (1), a series of other well-known taxans, such as taxol (2), cephalomanine (3), and their respective 10-deacetyl derivatives (4) and (5). The separation of (1) from the above taxanes requires a purification through column chromatography.

2R'=C ₆ H _S ;R*=C0CH ₃

•£R'=C ₆ H ₅ _ -=H

5R'=—C(CH ₃ ) _S CHCH ₃ ;R ^« =H

For this purpose silica gel is preferably used as the stationary phase. Solvent mixtures, consisting of an aliphatic hydrocarbon, for example n-hexane, cy- clohexane or n-heptane, or aromatic hydrocarbon, for example toluene, together with a higher polarity sol¬ vent, such as ethyl acetate or acetone are used as

eluentε.

The compound (1), once recovered from the chroma- tographic fractions containing it, is isolated after crystallization from whether acetone or diisopropyl ether or mixtures thereof with n-hexane or n-heptane.

The new compound (1) shows remarkable structural affinities with the antitumor drug taxol (2), from which it differs for the kind of side chain bonded at the 13-position of the taxane nucleus. Therefore, the compound (1) can be available, besides extraction from vegetal material, by semisynthesis through processes similar to the ones used for the production of taxol (2) (I. Ojima et al, Tetrahedron 48, 6985, 1992).

Due to the structural affinities between the com- pound (1) and taxol (2), a similar antitumor activity from the former could be expected.

Indeed, in vitro activity of (1) against several tumoral lines, for example the one relating to breast, lung, colon and ovary cancer, is comparable with the taxol's one, as reported in Table 1. However, the new taxane (1) surprisingly shows a higher activity than the taxol's one with respect to adriamicine (ADR) resi¬ stant tumor cells and to leukemic cells.

Table 1 - Comparison between taxane (1) and taxol (2) antiblastic activity on various tumoral lines (IC50, nM).

Tumor cells Taxane(l) Taxol(2)

L1210 (murine leukemia) 3.6±0.3 57.0±3.0

A121 (human ovarian) 8.6±0.4 6.3±0.3

A549 (human NSCLC) 3.9±0.3 5.4±0.5 HT-29 (human colon) 5.4±0.5 6.0±0.6

MCF7 (human breast) 2.2±0.1 4.3±0.5

MCF7-ADR (ADR resistant) 430±22 >1000

In in vivo studies, the compound (1), administered in aqueous solution containing Cremophor( ^R ), proved to be effective against tumors implanted into nude mice. Accordingly, the taxan (1) is expected to be used as antitumor drug for the treatment of liquid tumors and drug-resistant tumors, such as adriamicine-resistant tumors.

According to the active doses found in the animal, the dose of the compound (1) in man should be comprised between 150 and 250 mg/π.2 with cycles repeated at a two or three-week interval until the metastasis disappea- ranee.

The following example illustrates the preparation of the compound of the present invention. Example 1 Ester at 13-position of 5B.20-epoxy-l.2α.4.76.108.13a- hexahvdroxytax-ll-en-9-one 4,10-diacetate 2-benzoate with (2R.3S.-N-hexanoyl-3-phenylisoserine (formula 1)

50 kg of Taxus media cv Hicksii powdered bark were extracted at room temperature with 130 liters and sub¬ sequently three times with 80 liters of a 9:1 methylene chloride/methanol mixture, each extraction running 24 hours.

The gathered extracts were vacuum concentrated and the residue (4300 g) was taken up with 23 liters of a 9:1 toluene acetone mixture. After having filtered the insoluble matter, the solution was purified by column chromatography through 27 kg of silica gel, eluting with the same solvent mixture. The fractions containing the product (1) were gathered and evaporated to dryness under vacuum. The residue was crystallized from 80 ml of a 1:1 n-hexane/acetone mixture, 17,5 g of (1), m.p. 209 ^* , [α] _D - 42" (c = 0.3, MeOH), M+ a m/z 847, were obtained.

The spectrophotometric data of the compound (1) are the following: IR (nujol): 3500-3300, 1710, 1640 cm ^-1 UV (MeOH): 222 (13900), 232 (16250), 274 (1130), 282 (990) nm

CIMS (NH ₃ ), m z 865 (40%, M+NH ₄ ), 848 (10, MH), 586 (30, M+NH ₄ -279) ^-NMR (300 MHz, CDC1 ₃ , ppm, J in Hz) 5,66 (d, J = 7,0; H-2), 3,78 (d, J = 7,0; H-3), 4,93 (dd, ₁ = 9,4, J ₂ = 2,0; H-5), 2,54 (ddd, J = 15,5, J ₂ = 9,4, J ₃ = 6,6; H-6α), 1,84 (ddd, J ₁ = 15,5, J ₂ = 10,9; J ₃ = 2,0; H-6β), 4,39 (ddd, J = 10,9, J ₂ = 6,6, J ₃ = 4,1; H-7), 6,28 (s, H-10), 6,23 (t, J = 6,23; H-13), 2,24-2,32 (2H, m; H-14), 1,26 (s, H-16), 1,14 (s, H-17), 1,81 (d, J = 1,2; H-18), 1,67 (s, H-19), 4,17 (d, J = 8,6;

H-20α), 4,28 (d, J = 8,6; H-20β), 4,65 (dd, _± = 4,9, J ₂ = 2,5; H-2'), 5,56 (dd, J = 8,9, J ₂ 2,5; H-3'), 2,18 (t, J = 7,3; H-2"), 1,56 (m; H-3"), 1,28-1,20 (m; H-4" e H-5"), 0,83 (t, J = 6,7; H-6"), 8,10 (d, J = 7,8; PhCO H-2 e 6), 7,50 (t, J = 7,8; PhCO H-3 e 5), 7,61 (t, J = 7,8; PhCO H-4), 7,38 (m; 3'-Ph H-2,3,4,5,6), 2,34 (s, COCH3), 2,24 (s, COCH3) , 6,25 (d, J = 8,9; NH), 2,49 (d, J = 4,1; 7-OH), 1,84 (s, 1-OH), 3,55 (d, J = 4,9; 2'-OH). ¹³ C-NMR (75,43 Hz, CDCI3): 78,99 (C-1), 74,93 (C-2), 45,57 (C-3), 81,07 (C-4), 84,37 (C-5), 35,59 (C-6), 72,15 (C-7), 58,56 (C-8), 203,63 (C-9), 75,55 (C-10), 138,06 (C-ll), 142,05 (C-12), 72,29 (C-13), 35,59 (C-14), 43,18 (C-15), 26,79 (C-16), 21,86 (C-17), 14,81 (C-18), 9,54 (C-19), 76,46 (C-20), 172,78 (C-1'), 73,16 (C-2'), 54,53 (C-3'), 172,90 (C-1"), 36,55 (C-2"), 25,34 (C-3"), 31,29 (C-4"), 22,28 (C-5"), 13,83 (C-6"), 129,09 (PhCO C-1), 130,19 (PhCO C-2 e C-6), 128,68 (PhCO C-3 e C-5), 133,68 (PhCO C-4), 133,11 (Ph C-1), 126,94 (Ph C-2 e C-6), 128,93 (Ph C-3 e C-5), 128,23 (Ph C-4), 22,58 (COCH3), 20,84 (COCJK3), 171,23 (COCH3), 170,23 (CJQCH3), 166,95 (PhCO).

C ₄₆ H ₅₇ N0 ₁₄ : found% C = 65,11; H = 6,86; N = 1,60 calc.% C = 65,15; H = 6,78; N = 1,65.