A Second Generation Formal Synthesis of (−)-Cephalotaxine
作者:Abdul Hameed、Alexander J. Blake、Christopher J. Hayes
DOI:10.1021/jo801540q
日期:2008.10.17
A second generation formal synthesis of the alkaloid (-)-cephalotaxine has been achieved using an alkylidene carbene 1,5-CH insertion reaction to establish a key quaternary stereocenter. The carbene precursor was readily derived from L-proline, and the 1,5-CH insertion reaction was performed under Ohira's conditions using lithiotrimethylsilyldiazomethane (LTDM), which gave the desired spirocyclic product
The Combination of Diallylboration and Ring-Closing Metathesis in the Synthesis of Spiro-β-Amino Alcohols and (±)-Cephalotaxine
作者:Nikolai Yu. Kuznetsov、Galina D. Kolomnikova、Victor N. Khrustalev、Denis G. Golovanov、Yuri N. Bubnov
DOI:10.1002/ejoc.200800755
日期:2008.11
single-crystal X-ray analysis. The dehydrobromination of the tricyclic bromides with tBuOK produced olefins in good yields, which underwent allylic-type rearrangement in the presence of MgBr2·Et2O. Alkaline hydrolysis of the rearranged carbamates led to diastereomerically pure spiro-β-amino alcohols. The structure of the dimethyl-substituted amino alcohol was proved by single-crystal X-ray analysis. rac-(5R*