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α-Dibenzylamino- and α-benzyloxy- derivatives of N-acetyl-(S)-4-benzyl-5,5-dimethyloxazolidin-2-one readily undergo highly stereoselective boron mediated syn-aldol reactions with a range of aromatic and aliphatic aldehydes, generating the syn-aldol products in good to excellent yields as single diastereoisomers after purification. In the α-dibenzylamino series, deprotection of the functionalised aldol fragments to the corresponding α-amino-β-hydroxy methyl ester or α-amino-β-hydroxyaldehyde proved problematic, with a range of N- and O-protecting groups giving mixtures of products arising from endocyclic and exocyclic cleavage pathways. However, in the α-benzyloxy series, O-silyl protection of the aldol products, and subsequent DIBAL reduction gives stereoselectively the corresponding N-1′-hydroxyalkyloxazolidin-2-ones, which undergo base promoted fragmentation to the desired highly functionalised and differentially protected α,β-dihydroxyaldehydes in good yields and without loss of stereochemical integrity. © 2004 Elsevier Ltd. All rights reserved.

The propensity for N-Boc-4-hydroxymethyl-oxazolidin-2-ones to undergo rapid O-O and N-O carbonyl transfer makes these L-serine derived chiral auxiliaries unsuitable for attachment to polymers. © 2002 Elsevier Science Ltd. All rights reserved.

The synthesis of α-vinyl-β-hydroxyesters and α-ethylidene-β-hydroxyesters (β-substituted Baylis-Hillman products) via the dienolate aldol reaction of (E)-N-crotonoyl C(4)-isopropyl SuperQuat is described. High levels of syn-diastereoselectivity (up to >98% de) are observed for the dienolate aldol reaction with boron enolates, generated either directly with Bu2BOTf or by transmetalation of the potassium enolate with B-bromocatecholborane. Cleavage of the resultant syn-aldol products from the auxiliary gives α-vinyl-β-hydroxyesters in >98% de and >98% ee. Subsequent isomerisation of the double bond into conjugation provides α-ethylidene-β-hydroxyesters (β-substituted Baylis-Hillman products) in high diastereo- and enantiopurity (≥91:9 [(E):(Z)] and >98% ee). © 2009 Elsevier Ltd. All rights reserved.

Enolates of (S)-N,N′-bis-(p-methoxybenzyl)-3-iso-propylpiperazine-2,5-dione exhibit high levels of enantiodiscrimination in alkylations with (RS)-1-aryl-1-bromoethanes and (RS)-2-bromoesters, affording substituted diketopiperazines containing two new stereogenic centres in high de. Deprotection and hydrolysis of the resultant substituted diketopiperazines provides a route to the asymmetric synthesis of homochiral methyl 2-amino-3-aryl-butanoates and 3-methyl-aspartates in high de and ee. © 2006 Elsevier Ltd. All rights reserved.

A strategy for the asymmetric synthesis of homochiral [(R,R)- or (S,S)-], or meso-(R,S) bis-β-amino acid scaffolds, formally resulting from the stepwise conjugate addition of two differentially protected homochiral lithium amides to two α,β-unsaturated esters attached to a central arene, is demonstrated. Further manipulation enables the efficient synthesis of orthogonally protected pseudo-meso or pseudo-C2 symmetric scaffolds via selective N-benzyl or N-allyl deprotection, enabling regio-, stereo- and chemoselective functionalisation. © 2002 Elsevier Science Ltd. All rights reserved.