以高非对映异构体比[95:3]获得了外消旋合成结构单元(2 R *,3 R *)-3-甲基-4-(苯硫基)丁丹-2-醇(2 R *,3 R *)- 2。 5,(2 R *,3 R *)/(2 R *,3 S *)-比率是由路易斯酸催化的二甲基锌加成外消旋的2-甲基-3-(苯基硫烷基)丙醛(rac - 1)。由Chirazyme L-2(固定化南极假丝酵母脂肪酶B,CAL-B)催化的醋酸乙烯酯连续两次酰化反应导致四种立体异构体中的三种被优先酯化(2 S,3 S)98:2 dr和98%ee的)-3-甲基-4-(苯基硫烷基)丁-2-醇(2 S,3 S)-2。在第一个CAL-B催化的酰化步骤中获得的(2 R,3 R)-3-甲基-4-(苯基硫烷基)丁-2-醇(2 R,3 R)-2的立体异构不纯乙酸盐为使用CAL-A(固定的Novozyme SP 525)作为催化剂进行水解和再酯化,留下(2 R,3
作者:Alistair J. M. Farley、Christopher Sandford、Darren J. Dixon
DOI:10.1021/jacs.5b10226
日期:2015.12.30
The highly enantioselective sulfa-Michael addition of alkyl thiols to unactivated α-substituted acrylate esters catalyzed by a bifunctional iminophosphorane organocatalyst under mild conditions is described. The strong Brønsted basicity of the iminophosphorane moiety of the catalyst provides the necessary activation of the alkyl thiol pro-nucleophile, while the two tert-leucine residues flanking a
Convergent synthesis of a key intermediate for hypocholesterolemic agent 1233A, starting from methyl 3-hydroxy-2-methylpropanoate and asymmetrized bis(hydroxymethyl)acetaldehyde (BHYMA*)
作者:Giuseppe Guanti、Luca Banfi、Giovanna Schmid
DOI:10.1016/s0040-4039(00)73162-5
日期:1994.6
Compound 2, which is a known intermediate for the total synthesis of hypocholesterolemic agent 1233A 1, has been synthesized in good overall yield through a convergent approach, employing 3-hydroxy-2-methylpropanoate 6 and BHYMA* 5 as chiral building blocks.