Twelve pseudotetrapeptides, Boc-NHCH(CH2Ph)CH(OH)CH2CH(CH2Ph) CO-Xaa-Phe-NH2 9-11, were prepared by [(benzotriazol-1-yl)oxy]tris(dimethylamino)phosphonium hexafluorophosphate-mediated couplings of diastereoisomeric O-silylated (2R or 2S,4R or 4S,5S)-2-benzyl-5-(tert-butoxycarbonyl)amino-4-hydroxy-6-phenylhexanoic acids 1 with dipeptides H-Xaa-Phe-NH2 (Xaa = Gln, Glu(OBzl) or Ile) 3-5, followed by O-deprotection. Pseudotetrapeptides 9-11 were tested for inhibition of aspartic proteinases secreted by Candida albicans and C. tropicalis. The level of inhibition of both yeast proteinases was very low, contrasting with the nanomolar IC50 values obtained for inhibition of HIV-1 proteinase.