D. Crich et al., SYNTHESIS OF THE TAXOL AB-SYSTEM BY OLEFINATION OF AN A-RING C1 KETONE AND DIRECT B-RING CLOSURE, Tetrahedron, 53(21), 1997, pp. 7139-7158
Two syntheses of 13-deoxy-taxol C1 ketones are presented. Olefination
of these C1 ketones is achieved, indirectly, via either the Meyer-Schu
ster reaction or by introduction of a vinyl group with vinylcerium dic
hloride followed by allylic rearrangement. Both methods provide the E-
olefin exclusively. Dihydroxylation of these olefins is achieved with
catalytic OsO4 and NMNO in moderate yield, providing the taxol-1,2-dio
l unit with the correct relative stereochemistry. Closure of the B-rin
g is brought about in excellent yield by displacement of an allylic br
omide at C9 by an alpha-sulfonyl anion at C10. (C) 1997 Elsevier Scien
ce Ltd.