“Standardized intermediates” for oligosaccharide synthesis. Precursors of d-galactopyranose residues having chain extension at position 3, or positions 3 and 2
作者:Mina A. Nashed、Manjit S. Chowdhary、Laurens Anderson
DOI:10.1016/s0008-6215(00)88053-2
日期:1982.4
-galactopyranosides 6a–d . These were converted into the glycosyl halides by published methods. An improved preparation of allyl 2,6-di- O -benzyl-( 15 ) and 2,4,6-tri- O -benzyl-( 19 ) α- d -galactopyranoside was achieved. The direct acetonation of 1 to the 3,4- O -isopropylidene derivative 13 , followed by benzylation and mild acid hydrolysis, gave 15 in 56% yield. The transient protection of O-3 in 15
摘要一系列带有第二个苯甲酰基(8a,12a)或可选择性除去的临时保护基团(8b–d,2b)的2-O-苯甲酰基-4,6-二-O-苄基-α-d-吡喃半乳糖基卤化物。由烯丙基α-d-吡喃半乳糖苷(1)合成位置3处的12b)。关键中间体是1-丙烯基4,6-二-O-苄基-α-d-吡喃半乳糖苷(5),由1经4,6-O-亚苄基-2,3-二-O-巴豆基衍生物2制备。通过在低温下进行选择性酰化作用,依次引入2-O-苯甲酰基和各种3-取代基,得到完全取代的1-丙烯基α-d-吡喃半乳糖苷6a-d。通过公开的方法将它们转化为糖基卤化物。获得了改进的烯丙基2,6-二-O-苄基-(15)和2,4,6-三-O-苄基-(19)α-d-吡喃半乳糖苷的制备。将1直接乙酰化为3,4-O-异亚丙基衍生物13,然后进行苄基化和温和的酸水解,得到15,收率为56%。通过用(2-甲氧基乙氧基)甲基氯将二丁基亚锡衍生物16烷基化来完成1