Highly Diastereoselective Lithium Enolate Aldol Reactions of Butane-2,3-diacetal Desymmetrized Glycolic Acid and Deprotection to Enantiopure <i>anti</i>-2,3-Dihydroxy Esters
作者:Darren J. Dixon、Steven V. Ley、Alessandra Polara、Tom Sheppard
DOI:10.1021/ol016707n
日期:2001.11.1
[reaction--see text] The butane-2,3-diacetal (BDA) desymmetrized glycolic acid building block 1 undergoes efficient and highlydiastereoselective lithium enolate aldol reactions with both aromatic and aliphatic aldehydes to afford, after an acidic methanolysis deprotection step, the enantiopure anti-2,3-dihydroxy esters in good yield.
According to a chiral memory protocol, a chiral glycolic acid equivalent, the butane-2,3-diacetal-desymmetrized glycolate 2, is obtained from chiral 3-halopropane-1,2-diols 1. Compound 2 is a new and effective building block for the synthesis of mono- and dialkylated α-hydroxy acids 3, which constitute a biologically and pharmacologically important structural motif.
Preparation of enantiopure butane-2,3-diacetals of glycolic acid and alkylation reactions leading to α-hydroxyacid and amide derivatives
作者:Steven V. Ley、Elena Diez、Darren J. Dixon、Richard T. Guy、Patrick Michel、Gillian L. Nattrass、Tom D. Sheppard
DOI:10.1039/b412788a
日期:——
The preparation of butane-2,3-diacetal protected glycolic acid and related systems is described together with highly selective alkylationreactions of (R,R) and (S,S) butanediacetal protected glycolic acid. These compounds are readily deprotected to give enantiopure alpha-hydroxyacids, alpha-hydroxyesters or alpha-hydroxyamides by suitable choice of conditions.