Structural features of two taxoids from Taxus baccata L. growing in Turkey

As a part of our ongoing research of the taxane-type constituents from T. b accata L. (Taxaceae) recorded in the Flora of Turkey, 2 alpha, 5 alpha, 10 beta -triacetoxy-14 beta-(2-methyl)-butryloxy-4(20),11-taxadiene (I) and ta xusin (II) were isolated from the heartwood, in addition to the other taxoi ds. Their structures were elucidated using extensive spectroscopic techniqu es (IR, H-1 NMR, C-13 NMR, DEFT 135, H-1 H-1 COSY, HMQC, HMBC and MS). Mole cular mechanic calculations and conformational analysis of I and II have be en established using the MM3 program. The most probable conformation for co mpound I was obtained using semi-empirical molecular orbital methods and X- ray crystal structure results of II. Molecular orbital calculations of the derivative compound 4(20), 11-taxadiene (III) have been carried out to comp are semi-empirical and experimental knowledge about molecular geometries in gas phase and solid state. (C) 2001 Elsevier Science B.V. All rights reser ved.