Alternatively, the 1-propenyl intermediate was obtained directly by using 1-propenyl 2,4,6-tri-O-benzyl-alpha-D-galactopyranoside as the acceptor in the initial coupling reaction. An efficient 3-step synthesis of 10 was accomplished by the dibutyltin oxide-assisted, selective crotylation of allyl alpha-D-galactopyranoside at O-3, followed by benzylation and treatment of the product with potassium tert-butoxide
被保护的糖肽N-(苄氧羰基)-L-丙
氨酰基-[O-(2,3,4,6-四-O-苯甲酰基-β-D-
吡喃半
乳糖基)-(1-3)-O-(通过偶合2,4,6-三-O-苄基-α-D-
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乳糖(1 ---- 3)]-L-苏
氨酰基-
L-丙氨酸2,2,2-三
氯乙基酯各自的二糖和三肽嵌段。通过将四-O-苯甲酰基-α-
D-半乳糖吡喃糖基
溴化物偶联到烯丙基2,4,6-三-O-苄基-α-D-
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乳糖苷并将产物转化为O-(2,3,通过
1-丙烯基糖苷的4,6-四-O-苯甲酰基-β-D-
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乳糖基)-(1 ---- 3)-2,4,6-三-O-苄基-α-D-
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乳糖基
氯和游离的(1-OH)糖。或者,在初始偶联反应中,通过使用
1-丙烯基2,4,6-三-O-苄基-α-D-
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乳糖苷直接作为受体,获得
1-丙烯基中间体。通过在O-3处烯丙基α-D-
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乳糖苷的二丁基氧化
锡辅助的选择性丁酰化,然后进行苄基化和用
叔丁醇钾处