Stereoselective synthesis of β-substituted-l-threonines from enantiopure 5-acetyl-2-isoxazolines
作者:Giuseppe Cremonesi、Piero Dalla Croce、Alessandra Forni、Maddalena Gallanti、Concetta La Rosa
DOI:10.1016/j.tet.2011.02.055
日期:2011.4
ted (5S)- and (5R)-5-acetyl-2-isoxazolines were obtained from the corresponding racemic mixtures by means of an enzymatic reduction with baker’s yeast, followed by the separation of the enantiopure syn- and anti-alcohols and oxidation of the alcohol group. The reaction between these ketones and (2R)-Schöllkopf’s bislactim ether azaenolate was studied: using (5S)- and (5R)-3-methyl derivatives, two
通过用贝克酵母进行酶促还原,从相应的外消旋混合物中获得对映体纯的,3-甲基或3-乙氧基羰基取代的(5 S)-和(5 R)-5-乙酰基-2-异恶唑啉。对映纯顺式和反式醇的分离和醇基的氧化。这些酮和(2之间的反应- [R ) - Schöllkopf的bislactim醚azaenolate进行了研究:使用(5-小号) -和(5 - [R)-3-甲基衍生物,以良好的收率和立体选择性得到两个非对映体加合物,而反应(5 S)-和(5 R)-3-乙氧羰基衍生物导致产物的复杂混合物。随后吡嗪环的受控水解导致β-(3-甲基-4,5-二氢-异恶唑-5-基)-1-苏氨酸甲酯与相应的(R)-缬氨酸二肽一起。