62(P34) (-)-コレトールおよび(+)-コレトジオールの合成(ポスター発表の部)

概要

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Fourteen-membered bislactones, (-)-Colletol (1) and (+)-Colletodiol (2), were synthesized. Reductive ring opening reaction of ethyl (E)-(4R, 5R)-4,5-epoxy-2-hexenoate (16) with HCO_2H-Et_3N in the presence of Pd_2(dba)_3CHCl_3-PPh_3 catalyst gave ethyl (E)-(5R)-5-hydroxy-2-hexenoate (17) in 84% yield. Protection of the hydroxy group gave the ester 18, followed by hydrolysis gave the unsaturated acid 19. The ester 18 was converted to the epoxy unsaturated ester 21 in 4 steps, which was subjected the palladium-catalyzed reductive ring opening reaction with formic acid to give the alcohol 22 having a 1,3-syn diol system in 72% yield. After the ester 23 was converted to the allyl ester 24, the coupling reaction with 19 was carried out to give 25. Deprotection of the alcohol and reductive removal of the allyl ester, followed by cyclization and deprotection gave (-)-Colletol. Nucleophilic ring opening of the oxirane 21 with acetic acid was carried out stereoselectively with retention of stereochemistry to give 28 in 95% yield, which has the 4,5,7-trihydroxy moiety with different protection. The ester 29 was converted to the allyl ester 30, and coupling with 19 and cyclization as a similar procedure as above gave (+)-Colletodiol after deprotection. The palladium methods for preparing the alcohols from the oxiranes described above are considered to be useful for stereoselective construction of polyols.
天然有機化合物討論会の論文
1997-07-20