Highly enantioselective syntheses of α-hydroxyacids using N-benzyl-4,4,7α-trimethyl--octahydro-1, 3-benzoxazine as a chiral adjuvant
作者:Xu-Chang He、Ernest L. Eliel
DOI:10.1016/s0040-4020(01)87677-8
日期:1987.1
Addition of Grignard and organolithium reagents to as well as hydride reduction of 2α-benzoyl-N-benzyl-4,4,7α-trimethyl--octahydro-1 ,3-benzoxazine (2, Y = C6H5CO) and addition of phenylmagnesium bromide to the corresponding 2-acetyl analog (11) proceed in highly diastereoselective fashion to produce virtually exclusively the diastereomer predicted on the basis of Cram's chelate rule if chelation involves
添加格氏试剂和有机锂试剂,以及将2α-苯甲酰基-N-苄基-4,4,7α-三甲基-八氢-1,3-苯并恶嗪(2,Y = C 6 H 5 CO)氢化还原并添加如果螯合涉及环氧原子,则将苯基溴化镁与相应的2-乙酰基类似物(11)进行高非对映选择性的方式,实际上仅产生根据克拉姆螯合规则预测的非对映异构体。加合物的轻度酸水解,然后进行选择性氧化,可生成高对映体纯的对羟基酸,并且可以干净地回收手性佐剂。