Dilip R. Wagle

A novel chemical transformation of 3-vinyl-4-substituted-2-azetidinones

Abstract Transformation of α-vinyl-β-lactams involving an anti-Markovnikov addition reaction is described. The action of PdCl 2 CuClO 2 on the vinyl group leads to terminal aldehydes instead of the expected methyl ketones. The intermediate prepared by the reduction of this aldehyde group followed by conversion of the primary hydroxyl group to a chloro derivative was rearranged in good yield to a 1,2-diaryl-3-carbomethoxypyrrolidine.

Polyhydroxy Amino Acid Derivatives via β-Lactams Using Enantiospecific Approaches and Microwave Techniques

Abstract Enantiospecific synthesis has been developed for α-hydroxy β-lactams of predictable absolute configuration starting with readily available carbohydrates. Stereospecific approaches and microwave assisted chemical reactions have been utilized for the preparation of these 3-hydroxy-2-azetidinones and their conversion to natural or non-natural enantiomeric forms of intermediates for gentosamine, 6-epi-lincosamine, γ-hydroxythreonine, and polyoxamic acid.

Stereoregulated synthesis of β-lactams from schiff bases derived from threonine esters

Abstract A variety of optically active 3-substituted-2-azetidinones has been prepared by the annelation of Schiff bases derived from cinnamaldehyde and D-threonine esters and their absolute configuration determined. When the β-hydroxyl group of threonine is unprotected, both enantiomeric forms of N-unsubstituted 3,4-disubstituted-2-azetidinones can be prepared from a single β-lactam-forming reaction. On the other hand, by converting the hydroxyl group of D-threonine to a bulky group (e.g., triphenylsilyl ether), very high diastereoselectivity can be induced. The multiple functional groups on these β-lactams can be easily modified to generate useful synthons for optically active sugars, alkaloids, and monocyclic and bicyclic β-lactam antibiotics.

Enantiospecific synthesis of β-lactams via cycloaddition

Enantiospecific synthesis of variously substituted cis-β-lactams can be achieved by the annelation of Schiff bases from optically active ketal aldehydes derived from D-threonine. Similar annelation of Schiff bases from the triphenylsilyl ether of D-threonine ester and cinnamaldehyde leads to cis-β-lactams with high diastereofacial selectivity.

Antipodal forms of β-lactams via stereospecific reactions

Abstract 3,4-Disubstituted-1-aryl-2-azetidinones of interest for rearrangement to various natural products were prepared by enantiospecific synthesis and their functional groups and absolute configuration were manipulated by stereospecific reactions to produce antipodes.

Absolute configuration of α-substituted β-lactams from D-glyceraldehyde acetonide

3,4-Disubstituted-1-arylazetidin-2-ones can be prepared in an enantiospecific manner by the annelation of Schiff bases from optically active glyceraldehyde acetonide and their stereochemistry determined from n.m.r. studies on lactones prepared from these β-lactams by molecular rearrangement.

Studies on lactams. Part 74. An approach to the total synthesis of amino sugars viaβ-lactams

Convenient intermediates for mono- and di-amino sugars related to antibiotics can be prepared in a stereocontrolled fashion by the rearrangement of 3,4-disubstituted azetidin-2-ones which in turn can be synthesized by stereoselective annelation of certain imino compounds by substituted acetic acid derivatives.

Reactions of hydrazides and hydrazones with n-butyl-lithium

Aromatic hydrazides give indazol-3(2H)-ones in good yield when treated with 3 equivalents of n- butyl-lithium;aliphatic and heterocyclic hydrazides afford the corresponding aldehydes under the same conditions.

Novel synthesis of optically active morpholines

Morpholines have been synthesized by an efficient molecular rearrangement of appropriate derivatives of α-hydroxy-β-lactams including optically active β-lactams prepared from homochiral Schiff bases.