61 フミトレモルジンBおよび関連化合物の合成

概要

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Total synthesis of fumitremorgin B, tremogenic micotoxin, from tryptophan is described. The Pictet-Spengler reaction of the 6-methoxy-L-tryptophan (1b) and 3-methyl-3-phenylthiobutanal in the presence of trifluoroacetic acid gave the cis-β-carboline (10b) in 58% and the trans-isomer (11b) in 20% yields. Condensation of 10b with trichloroethoxycarbonyl-L-proline chloride gave the dipeptide (12b) in 92% yield. Dehydrogenation of 12b with DDQ followed by dehydrosulfenylation gave the endo olefin (20b) as the major product and the exo isomer (21b) as the minor product. Reductive deprotection and cyclization of 20b resulted in the formation of the key intermediate (22b) in 84% yield. Treatment of 22b with NBS in aqueous THF gave the trans diols, (23b) as the major product in 77% and (24b) as the minor product in 10% yields. After the prenylation of the major trans isomer 23b,the oxidation of 18b with DDQ followed by the reduction with sodium borohydride gave the desired fumitremorgin B (28b). The selective and direct cis-hydroxylation was achieved by treating 22b with osmium tetraoxide to give the diol (30b) which was readily prenylated to yield fumitremorgin B (28b). All spectral data of the synthetic 28b were indistinguishable from those of natural specimen.
天然有機化合物討論会の論文
1986-09-09