Diastereoselective Additions of Titanium Enolates from N-Glycolyl Thiazolidinethiones to Acetals
摘要:
The stereochemical outcome of the Lewis acid-mediated glycolate addition of the titanium enolates from protected N-hydroxyacetyl-4-isopropyl-1,3-thiazolidine-2-thiones to dimethyl and dibenzyl acetals depends on the hydroxyl protecting group. Particularly, the pivaloyl protected glycolate derivative provides the reluctant anti adducts in high yields and diastereomeric ratios, which can be isolated and further converted in enantiomerically pure form to beta-methoxy or beta-benzyloxy alpha-pivaloyloxy carbonyl fragments in a straightforward manner.
A highly diastereocontrolled alkylation at the C-4 position of 4-acetoxyazetidin-2-one (5) employing chiral tin(II) enolates of heteroatom-substituted acetyl derivatives (3a–e) furnishes new synthetic intermediates (6a–e) for 1β-heteroatom-substitutedcarbapenems (2).
Azetidin-2-one derivatives and process for production thereof
申请人:LEDERLE (JAPAN) LTD.
公开号:EP0213610A1
公开(公告)日:1987-03-11
An azetidin-2-one derivative represented by the following formula (I)
wherein R' represents a hydrogen atom, a lower alkyl group, an aryl group, an aralkyl group, a lower alkoxy group, aralkoxy group, a lower alkylthio group, an aralkylthio group, or a substituted amino group, R2 represents a hydrogen atom, a lower alkyl group, an aryl group or an aralkyl group, and R3 represents a hydrogen atom or a group of the formula
In which R4 represents a hydrogen atom or a protective group for the hydroxyl group; and a process for production thereof.
The stereochemical outcome of the Lewis acid-mediated glycolate addition of the titanium enolates from protected N-hydroxyacetyl-4-isopropyl-1,3-thiazolidine-2-thiones to dimethyl and dibenzyl acetals depends on the hydroxyl protecting group. Particularly, the pivaloyl protected glycolate derivative provides the reluctant anti adducts in high yields and diastereomeric ratios, which can be isolated and further converted in enantiomerically pure form to beta-methoxy or beta-benzyloxy alpha-pivaloyloxy carbonyl fragments in a straightforward manner.