Bioorgmic & Uedichl Chemistry Leaws, Vol. 4. No. 2, pp. 233236.1994 Copyright a 1994 Elsevier Science Ltd Printed in Great Britain. Au rights reserved 0960-394X,94 $6.O@tO.00 0960-894X(93)EOO64-8 SYNTHESIS OF 19-HYDROXY DOCETAXEL FROM A NOVEL BACCATIN Rodolphe Margraff, Daniel B&.ard, Jean Dominique Bourzat and Alain Commercon*
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`Rh&e-Povlenc Rorer S.A.
`13, Quai Jules Guesde
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`BP14
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`de Recherches de Vitry-Alfortville
`94403 Vitry-w-Seine
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`Taxus Baccata.
`Abstract: The synthesis of 19-hydroxy docetaxel is described starting from a new baccatin derivative, 4, which was extracted from the needles of
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`This analog exhibits a high level of cytotoxicity in
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`experimental models. Dccetaxel (Taxotere@), 1, is a promising anticancer agent currently under phase II clinical trialsl. Dccetaxel is prepared from lo-deacetyl baccatin III, 2, which is extracted from the needles of
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`Taxus baccata.
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`This
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`renewable source of 2 makes docetaxel more available than natural paclitaxel (Taxol@), 3, which must be harvested from the bark. 1, RI = tBuOC0, R2 = H (docetaxel) 2,R=H 3, RI= CeH5C0, R2 = Ac (paclitaxel) 4,R=OH In our search for new biologically active taxoids and crucial information on structure-activity relationships, we looked for other minor baccatins besides the most abundant compound, 2, in Tanrs
`most profuse congener, which cocrystallized with 2 with a relative abundance of a few percent (usually 3 to 5% although concentrations as high as 20% were found in some samples) was identified as lo- deacetyl-19-hydroxybaccatin III (4)z.j. This new baccatin derivative which probably originates from lo- deacetylbaccatin III through a further biosynthetic oxidation step, was isolated by preparative HPLC on a 75X25 cm Amicon Cl8 bonded 20 microns 100 A phase column. For injection, 6.6 g of a crude extraction baccatin mixture was absorbed by vacuum evaporation on 75 g Cl8 Bondesil 40 microns silica gel and loaded in a 5x7 cm precolumn. Isocratic elution with MeOH/H20 : 47/53 (v/v) afforded 0.08 g of lo-acetyl- 19-hydroxybaccatin III, 4.
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`needles. The
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`baccata
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`234 R. MARGRAFF et al. Related 19-hydroxylated baccatins have been previously described in the literature as constituents of Tarus baccata4 and other Taxus species such as Tams chinensid, Taxu yunnanensis6 and Tmw wallichiana? 4 5 6
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`a
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`iii
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`.&NH 0 9 -- % 10 Reagents: (i) CCl3CH2OCOCl (5eq.), CsHsN, 2OY!, 3h. (ii) 7 (l..kq.), DCC (U+.), DMAP (OSeq.), toluene, 8O”C, 2h. (iii) a) HCOOH, 2O”C, 4h., b) @o&O, CHzCl2, NaHC03, 20°C, iv) Zn, AcOH, MeOH, 60°C. lh.
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`Synthesis of 19-hydroxy docetaxel 235
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`This original structure prompted us to prepare the corresponding docetaxel analog. Because of the
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`uncommon position of the hydroxyl group at C-19, we might expect better water solubility for this analog with possible favorable effect on the antitumoral activity spectrum. The enantioselective access to the corresponding docetaxel analog was achieved by analogy to our previously published methodology7. The pentahydroxy compound 4, was first 0-tri-protected using 2,2.2- trichloroethoxycarbonyl chloride CTrocCl) in pyridine. Surprisingly, acylation of hydroxyl groups at C-7 and C-10 occurmd spontaneously while acylation at C-19 was partial and difficult to complete even in the presence of a large excess of chloroformate in pyridine at reflux (64% of acylated products was obtained at room temperature for 3h. with a 5:6 ratio of 53). Although this 0-tri-protection step has not yet been optimized, we were able to complete the synthesis without further difficulty. Esterification of the O-tri- protected baccatin derivative 5 using acid 7 gave under stamkd conditions ester 8 in excellent yield (98%). Deprotection of the oxaxolidine-type protection under acidic conditions followed by N-acylation of the intermediate phenylisoserka te with di-text-butyl dicarbonate afforded 9 in 60% overall yield. The final reductive deprotection was performed with zinc powder in acetic acid to give, after purification, 19-hydroxy- docetaxel,
`2 &ml for d&axe1 after 1 h at room temperature). This new taxoid was evaluated as an antitumor agent in experimental models. Different in vitro assays have been used to determine the activity of doc&axel and paclitaxel congeners on tubulin including inhibition of binding of labelled docetaxel or paclitaxel to microtubuless, promotion of microtubule assembly in the absence of GTPs and inhibition of microtubule disassembly at 4T9. The two last methods generally give the same results and the latter one was used here because of its rapidity. Compound 10 has been proven very active as an inhibitor of microtubule disassembly at 4°C ~D~O(lO)/IDSO@aclitaxel) = 0.4, while ID~O(docetaxel)/ID~O(paclitaxel) = 0.61; in addition this compound was cytotoxic against P388 leukemia cells (ICSO = 0.07 &ml). . . These results demonskate that c$emical at C-19 can be v * . B. Compound 4 is currently used in our laboratory to obtain further information on structure activity-relationships.
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`10, in
`42% yield. Compound
`10
`is less soluble than docetaxel in most of the organic solvents but, as expected, the additional hydroxyl function on the taxane skeleton improves the water solubility (measured 12 p@ml for
`versus
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`10
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`Acknowledgemen&:
`We thank Dr M. Vuilhorgne and 0011. for &uctuml analyses, Drs C. Combeau and J.F. Riou for biological evaluation and Mrs A. Gerbaud and E. Bouley for tech&al contribution.
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`References and notes:
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`1993,2(6), 627; Lavelle
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`F., Gueritte-Voegelein F., Gtknard D., Bull. Cancer, 1993.80,326. 2. Stnztuml data for compound 4 can be compared to those reporkd for 19-hydroxybaccatin III, see: McLaughlin J.L., Miller R.W., Powell R.G., Smith C.R., Jr.,J. Nut. Prod,
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`1981,44,312.
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`3. All new compounds exhibited
`IR, 1H and 1X-NMR spectra, mass spectral and combustion data in agreement with the structures indicated.
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`1. Lavelle F.. Cur-r. Opin. Inwt. Drugs,
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`236 R. MARGRAFF et al. 4: 194.7”C (AcOEt), mp: [aID -58 (c 0.16, tetrahydrofuran), IH-NMR (4OOMHz; DMSG d6): 6 0.97 and 1.17 (two s, 6H, C-l6H3 and C-17H3), 1.55 (bdd, lH, C-6H), 1.90 (s, 3H, C-18H3), 2.10 (m, 2H, C-14H2), 2.25 (s and m, 4H, C-6H and COCH3), 3.80 (d, lH, J=7 Hz, C-3H), 4.08 (m, 2H, C-20H and C-7H), 4.35 (d, lH, J=9 HZ, C-20H), 4.42 and 4,5 (AEX, 2I-L C-19H2OH). 4.65 (m, 2H, C-19HzOu and C-13H), 4.95 (bd, lH, C-5H), 5.07 (bs, lH, C-1OH). 6.5 (d, lH, 5~7 Hz, C- 2H), 7.57, 7.68 and 8.08 (t, t and d, 2H, 1H and 2H, J=8 Hz, OCOCsH5). 5: foam, [C&20 -34 (c 0.47, MeOH), lH-NMR (300 MHz; CDC13); 6 1.15 and 1.29 (two s, 6H, C-l6H3 and C-17H3), 1.87 (m, lH, C-6H), 2.15-2.40 (m, 2H, C-14H2), 2.19 and 2.35 (two s, 6H, C-l8H3 and OCOCH3), 2.70 (m, lH, C-6H), 4.10 (d, lH, J=7 Hz, C-3H), 4.20 (d, lH, J=8 Hz, C-20H), 4.42 (d, 1H. J=8 Hz, C-20H), 4.62 and 4.95 (26, 1H each, J=12 Hz, OCOO-CHz-CCl3 at C-7), 4.75 and 5.03 (2d, 1H each, J=12 Hz, OCOO-CH2-CC13 at C-19), 4.78 (limit ab, 2H, J=ll Hz, OCOG-CH2-CC13 at C-lo), 4.90 (m, lH, C-13H), 5.03 (bd, lH, J=lO Hz, C-5H), 5.46 (limit ab, 2H, C-19H,$, 5.66 (dd, 1H. J=ll and 8.5 Hz, C-7H), 6.28 (s, lH, C-lOH), 6.41 (d, lH, J=7 Hz, C-2H), 7.49, 7.63 and 8.13 (t, t and d, 2H, 1H and 2H, J=7.5 Hz, OCOCgH5). 6: foam, [C&)20 -29 (c 0.54, MeOH), lH-NMR (300 MHz; CDC13); 6 1.15 and 1.27 (two s, 6H, C-l6H3 and C-17H3), 1.87 (m, lH, C-6H), 2.15-2.35 (m, 2H, C-14H2), 2.20 and 2.35 (two s, 6H, Cl8H3 and OCGCH3), 2.63 (m, lH, C-6H), 4.00 (d, lH, J=7 Hz, C-3H), 4.38 (d, lH, J=8 Hz, C-20H), 4.45 (d, lH, J=8 Hz, C-20H), 4.65 and 4.95 (2d, 1H each, J=12 Hz, OCGG-CH2-CC13 at C-7), 4.70- 4.95 (m, 2H, C-19H$, 4.82 (limit ab, 2H, ‘OCOO-CH2-CC13 at C-lo), 4.90 (m, lH, C-13H), 5.03 (bd, lH, J=lO Hz, C-5H), 5.62 (dd, lH, J=ll and 8.5 Hz, C-7H), 6.30 (s, lH, C-lOH), 6.64 (d, lH, J=7 Hz, C-2H). 7.49, 7.63 and 8.15 (t, t and d, 2H, 1H and 2H, J=7.5 Hz, OCOCbH5). 18: foam, [a]$0 -39 (c 0.52, MeOH), lH-NMR (400MHz; DMSO d6): 6 0.98 and 1.17 (two s, 6H, C-l6H3 and C-17H3), 1.33
`9H, tBu), 1.51 (dd, lH, 5~13 and 12 HZ, C-6H), 1.59 and 1.83 (two dd, 1H each, J=15 and 9 Hz, C-14H2), 1.7 (s, 3H, C-l8H3), 2.22 (mt, lH, C-6H), 2.23 (s, 3H, GCGCH3). 3.61 (d, 1H. J=7 Hz, C-3H). 3.98 (mt, lH, C-7H), 4.01 (d, lH, J=8 Hz, C-20H), 4,11 (d, 1H. J=8 Hz, C20H), 4.32 (mt, lH, C-2’H), 4.38 and 4.48 (two dd, 1H each, J=12 and 5 Hz, C-19Hz), 4.87 (mt, lH, C-3’H), 4.92 (d, lH, J=lO Hz, C-5H), 5.0 (d, lH, J=lS Hz, C-IOH), 5.83 (t, lH, J=9 Hz, C-13H), 6.5 (d, lH, J=7 Hz, C-2H), 7.13, 7.27 and 7.34 (t, d and t, lH, 2H and 2H, J=7.5 Hz, CsHs), 7.42 (d, HI, J=9 Hz, NHCO), 7.6,7.68 and 7.98 (t, t and d, 2H, 1H and 2H, J=7.5 Hz, OCGCaH5). 4. Chauvike G., Guknatd D., Picot F., S6nilh V., Potier P., C. R. Skances Acad. Sci. Park, (s&e 2), 1981, 293,501. 5. Jia Z., Zhang Z., Chin. Sci. B&L, 1992,91, 1967; Zhang 2.. Jia Z., Huaxue Xuebao, 1992,49, 1023. 6. Zhang Z., Jia Z., Phytochem&ry, 1982,90,3673. 7. Commeqon A., I3katx-i D., Eknard F., Eourzat J.D., Tetrahedron Z&t., 1992,33, 5185; Boumt J.D. and Commeqon A., Tetrahedron Lett., in press. 8. Pamess J., Kingston D.G.I., Powell R.G., Harracksingh C., Horwitz S.B., Biochem. Biophys. Res. Commun., 1982,10.5,1082. 9. Lataste H., S&nilh V., Wright M., Guknard D., Potier P., Proc. Natl. Acad. Sci. U.S.A., 1984,81,4090. ’ (Received in Belgian 16 Augwt 1993)
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