Improved synthesis of d-allothreonine derivatives from l-threonine
摘要:
The improved synthesis of protected D-allothreonine derivatives [Fmoc-D-alloThr(Bu-t)-OH (1) and Fmoc-D-alloThr-(OBu)-Bu-t (2)] is described. The epimerization of cheap L-threonine (L-Thr) (3) with catalytic salicylaldehyde afforded a mixture of L-Thr (3) and D-alloThr (4) and separation of ammonium salt gave D-alloThr (4) in 96% de. The chemoselective deprotection of tert-butyl ether or tert-butyl ester of Fmoc-D-alloThr(Bu-t)-(OBu)-Bu-t (5) easily succeeded in converting Fmoc-D-alloThr(Bu-t)-OH (1) or Fmoc-D-alloThr-(OBu)-Bu-t (2), respectively. (C) 2013 Elsevier Ltd. All rights reserved.