4 Acanthacerebroside A並びに関連海産スフィンゴ糖脂質の立体化学(口頭発表の部)  [in Japanese] 4 STEREOCHEMISTRY OF ACANTHACEREBROSIDE A AND A RELATED MARINE SPHINGOGLYCOLIPID  [in Japanese]

In our study on the isolation and structure elucidation of biologically active compounds from marine invertebrates, we synthesized the four diastereomers of C_<16>-phytosphingosine (10, 12, 25, and 26), acanthacerebroside A (1), and D-galactosylceramide (3b) as described below. (2S, 3S)-Allylic alcohol, which was prepared from the L-serine derivative and the (E)-vinylalane compound, was converted into (2S, 3S, 4R)- and (2S, 3S, 4S)-phytosphingosines by epoxidation, DIBAH reduction, and debenzylation. The same treatment of (2S, 3R)-allylic alcohol gave (2S, 3R, 4R)- and (2S, 3R, 4S)-phytosphingosines. (2R)-Acetoxytetracosanoic acid was prepared and coupled to (2S, 3S, 4R)-phytosphingosine to give the ceramide (34). Glycosylation of 34 gave the desired monoglycoside (36) and the bisglycoside (37). 36 was converted into 1 by deacetylation. New D-galactosylceramides were isolated from Chondropsis sp., but the absolute stereochemistry has not been determined. Therefore, (2S, 3S, 4R, 6E)- and (2R, 3R, 4R, 6E)-phytosphingosines were prepared via asymmetric epoxidation. The former was transformed to (2S, 3S, 4R, 6E, 2'R)-D-galactosylceramide and its heptaacetate. The spectral data of them were in excellent agreement with those of the natural specimens.