Abstract: A novel class of D-Threo-1-phenyl-1-trifluoroacetamido-1, 3-propanediols wherein the benzene ring is substituted in the para-position by methylmercapto or methanesulphonyl and the hydroxy moiety at position 3 of the prepanediol is acylated to afford alkanoyloxy, halo-alkanoyloxy or aminoalkanoyloxy.The instant products are prepared: (1) by treating a D-threo-1-(p-methanesulphonylphenyl)-2-amino-1,3-propanediol or a D-threo-1-(p-methylmercaptophenyl)-2-amino-1,3-propanediol with trifluoroacetic acid or with an ester derivative thereof; (2) by oxidation of the mercapto moiety in a D-threo-1-(p-methylmercaptophenyl)-2-trifluoroacetamido-1, 3-propanediol to afford the corresponding 1-(p-methanesulphonyl) derivative; or (3) by esterification of the 3-hydroxy moiety in a D-threo-1-phenyl-2-trifluoroacetamido-1, 3-propanediol precursor.