Fujita S, Numata M, Sugimoto M, Tomita K, Ogawa T
Tokyo Research Institute, MECT Co., Saitama, Japan.
Carbohydr Res. 1994 Oct 17;263(2):181-96. doi: 10.1016/0008-6215(94)00155-3.
Regio- and stereo-selective glycosylation of a sialyl donor 6 that carries a N-phthaloyl protecting group at C-5 with a lactosyl acceptor 7 armed with a pivaloyl group at O-2a was performed to give the expected glycotrioside 5. Subsequent glycosylation of 5 with 2-azido galactosyl donor 4 gave glycotetraosyl derivatives 18 and 19. After conversion of 18 into imidates 25 and 26, coupling with (2S,3R,4E)-3-O-benzoyl-2-N-tetracosanoylsphingenine (2) was executed to afford completely protected ganglioside analogues 27 and 28. Selective cleavage of the methyl ester and N,O-deprotection gave the target de-N-acetyl GM2 (1).
用在O-2a位带有新戊酰基的乳糖基受体7对在C-5位带有N-邻苯二甲酰保护基的唾液酸供体6进行区域和立体选择性糖基化反应，得到预期的三糖糖苷5。随后用2-叠氮基半乳糖基供体4对5进行糖基化反应，得到四糖基衍生物18和19。将18转化为亚氨酸酯25和26后，与(2S,3R,4E)-3-O-苯甲酰基-2-N-二十四烷酰基鞘氨醇(2)偶联，得到完全保护的神经节苷脂类似物27和28。甲酯的选择性裂解和N,O-脱保护得到目标脱-N-乙酰基GM2(1)。
