TETRAHEDRON LETTERS Tetrahedron Letters 41 (2000) 7577–7581 Pergamon Polymer supported oxazolidin-2-ones derived from L-serine—a cautionary tale Sean P. Bew, Steven D. Bull and Stephen G. Davies* The Dyson Perrins Laboratory, University of Oxford, South Parks Road, Oxford OX13QY, UK Received 14 June 2000; accepted 28 July 2000 Abstract The capacity of N -Boc-4-hydroxymethyl-oxazolidin-2-ones to undergo rapid O–O and N–O acyl transfer makes these serine derived chiral auxiliaries unsuitable for attachment to polymers. © 2000 Elsevier Science Ltd. All rights reserved. There is currently much interest within the synthetic community directed towards the development of polymer supported chiral auxiliaries for the asymmetric synthesis of libraries of homochiral compounds. 1 Within this area, a number of homochiral polymer bound oxazolidin- 2-ones derived from tyrosine and serine and attached through the side-chain hydroxyl function- ality have been described, 2 although the key issue of polymer recyclability has not been addressed. 3 As recognised by Allin and Shuttleworth, 2a serine derived oxazolidin-2-ones have the potential for polymer support via attachment of the side-chain hydroxyl group of 1 to Merrifield resin. They have reported that polymer 3 may be employed for the asymmetric synthesis of carboxylic acid 4 in 42% yield and 96% e.e. (Scheme 1). 2a Scheme 1. Allin and Shuttleworth’s synthesis of polymer bound oxazolin-2-one derived from L-serine. Reagents and conditions: (i) KH (1.5 equiv.), DMF, 0°C; Merrifield resin, 18-crown-6 (cat.), 80°C, 5 days; (ii) dil. HCl, CH 2 Cl 2 , D, 6 h; (iii) (CH 3 CH 2 CO) 2 O, DMAP (10%), Et 3 N, THF, D, 4 days; (iv) LDA (2 equiv.), THF, 0°C; BnBr (2 equiv.); NH 4 Cl (aq.); (v) LiOH, THF, H 2 O * Corresponding author. 0040-4039/00/$ - see front matter © 2000 Elsevier Science Ltd. All rights reserved. PII:S0040-4039(00)01301-0