Ley SV, Dixon DJ, Guy RT, Palomero MA, Polara A, Rodriguez F, Sheppard TD. Studies on the generation of enolate anions from butane-2,3-diacetal protected glycolic acid derivatives and subsequent highly diastereoselective coupling reactions with aldehydes and acid chlorides.
Org Biomol Chem 2004;
2:3618-27. [PMID:
15592620 DOI:
10.1039/b412790k]
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Abstract
Highly diastereoselective coupling reactions of enolates derived from butane-2,3-diacetal protected glycolic acids 1 and 2 and their alkylated derivatives with aldehydes are reported together with their efficient acid-catalysed deprotection to yield enantiopure anti-2,3-dihydroxyesters. A procedure to provide the corresponding syn-2,3-dihydroxyesters is also described in two cases, proceeding via an acylation-reduction sequence. An usual double addition reaction of butane-2,3-diacetal protected glycolic acid to small aliphatic acid chlorides provides a synthetically useful, densely-functionalised lactone after acidic deprotection.
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