Synthesis and crystal structure of 2-debenzoyl and 4-deacetyl 1-deoxybaccatin VI derivatives

Two novel 4-deacetyl and 2,4-deacyl 1-deoxybaccatin VI derivatives were prepared from 1-deoxybaccatin VI. Their structures were elucidated using extensive spectroscopic techniques (IR, 1HNMR, DEPT, COSY, HMQC and MS). In addition, the conformations for these compounds were obtained by X-ray diffraction methods. Comparisons to 1-deoxybaccatin VI and paclitaxel identify relative differences principally in the cyclohexenyl ring (A ring). Conformational analysis showed that removal of 4-acetyl or 2,4-diacyl moiety has a decisive influence on the conformation of the A ring.