The protected serine aldehyde 10 was converted to the crystalline N-Boc-protected sphingosines 6–9 by a three-step reaction sequence. Compound 10 was transformed with high diastereoselectivity (95%) either to the erythro- or threo-alkynols, 17 and 18, respectively. The erythro-isomer 17 is formed by the addition to 10 of lithium pentadecyne 16 in THF/HMPT at −78°, whereas the corresponding threo-isomer
受保护的
丝氨酸醛10转化为结晶Ñ -Boc保护的
鞘氨醇6 - 9通过3步反应序列。将化合物10以高非对映选择性(95%)转化为分别为赤型或苏型
炔烃17和18。的赤式异构体17通过加入形成为10
锂pentadecyne的16在THF / HM
PT在-78℃,而相应的苏式异构体18在ZnBr的存在下制备2在Et 2 O中。
缩醛部分的脱保护得到1,3
-二醇19和20。通过在Lindlar催化剂上进行部分加氢,将这些二醇用Red-Al选择性还原为(E)-
鞘氨醇6和8或(Z) -异构体7和9。N- Boc基团的裂解和进一步转化为神经酰胺很容易实现,这是通过将6转化为N-
十八烷酰基-D-赤型-
鞘氨醇5来实现的。