New isocyanates from amino acids

New di- and polyisocyanates were synthesized from a-amino acids. The reaction route included the preparation of alpha-isocyanatoacyl chlorides from the corresponding amino acids and trichloromethyl chloroformate and their conversion into diisocyanato diesters by reaction with silylated alcohols. For comparison, 3-isocyanatopropanoyl chloride was also prepared by reaction of the O-silylated p-alanine with 4,4'-methylene bis(phenylisocyanate) and subsequent conversion of the isocyanatosilyl ester with thionyl chloride. Ethanediol, the isomeric propanediols, 1,4-butanediol, 1,6-hexanediol and glycerol were the alcohol components. The amino acids glycine, L- and DL-alpha-alanine, L-leucine, and L-phenylalanine were investigated. Some polyurethanes made from the isocyanates and several polyols were characterized by mechanical testing and thermomechanical analysis. The degradation behaviour was evaluated as a preliminary investigation. The new monomers may be useful candidates for the preparation of degradable polyurethanes for medical applications. (C) 1997 Elsevier Science Ltd.