135(P-86) コロカシンCの合成研究(ポスター発表の部)

概要

論文の詳細を見る
Crocacins A-D were isolated from Chondromyces crocactus and Chondromyces pediculatus and their relative stereochemistry is reported by R. Jansen et al. Herein we report the synthetic works to determine the absolute stereochemistry of Crocacin C. Starting with 1,3-propanediol, the allylic alcohol 2 was prepared in 5 steps. Sharpless asymmetric epoxidation was carried out using (-)-DET followed by Swern oxidation and Wittig olefination to give optically active alkenyl oxirane 4. Reductive opening of the oxirane was carried out regio- and stereoselectively using HCO_2H in the presence of Pd_2(dba)_3CHCl_3-PPh_3 as a catalyst to give the chiral homoallylic alcohol 5 with high enantioselectivity. Methylation of hydroxy group followed by deprotection to terminal alcohol and oxidation gave the aldehyde 6, which was subjected to phenylation and dehydration to give 7. Reduction of 7 was carried out with DIBAH to give allylic alcohol 8. The Second Sharpless epoxidation from 8 to 9 was carried out with (+)-DET followed by Swern oxidation and Emmons-Horner reaction using Ando's reagent to give (Z)-alkenyloxirane 10. Reductive epoxide opening was carried out with Pd_2(dba)_3CHCl_3-Pbu_3 to give 11 which has and stereochemistry at C-6 and C-7. The ester was converted to methyl ketone 12 in 3 steps, which is considered to be a synthetic precorsor of the Crocacin C.
2000-10-01