作者:Junlong Xiong、Zhichao Lu、Ning Ding、Sumei Ren、Yingxia Li
DOI:10.1002/ejoc.201300575
日期:2013.9
The synthesis of the pentasaccharide moiety of thornasteroside A, the first asterosaponin isolated from starfish in 1978 has been achieved for the first time. Initially, a [3+2] convergent strategy was attempted, but the β(14) glycosidic linkage between galactopyranose (sugar IV) and xylopyranose (sugar II) was formed with a low stereoselectivity and in low yield. Subsequently, a [3+1+1] strategy was
1978年从海星中分离出的第一个星皂苷,首次实现了刺甾酮A的五糖部分的合成。最初,尝试了 [3+2] 收敛策略,但在吡喃半乳糖(糖 IV)和吡喃木糖(糖 II)之间形成的 β(14) 糖苷键具有低立体选择性和低产率。随后,采用了 [3+1+1] 策略。吡喃半乳糖供体 (18) 在 2 位配备有相邻的参与 Lev (乙酰丙酰基) 基团,首先与三糖受体偶联以构建 β(14) 糖苷键。然后选择性地去除 Lev 基团,随后用过苯甲酰化的 D-吡喃岩藻糖施密特供体进行糖基化,有效地得到所需的五糖。