A versatile synthetic route to 1,5-dithiocins from o-mercapto aromatic aldehydes

An earlier procedure for the facile preparation of benzo-fused 1,5-dithioci ns 2a-2c from o-mercaptobenzaldehydes has been improved and shown to be cap able of extension to the preparation of several naphthalene-derived analogu es. The general method also afforded several N-alkylated 1,5-dithiocins 4, 5 by replacing NH3 with the appropriate primary amine. It was found that N- acylation of the 1,5-dithiocins was successful only with methyl chloroforma te. Attempted N-phenylation met with limited success but was shown to be un necessary since even the less reactive aniline readily undergoes the genera l reaction of primary amines. When simple a-amino acids, or their methyl es ters, were employed as the primary amine in the reaction with o-mercaptoben zaldehyde, the formation of the N-alkylated 1,5-dithiocins 4a, 17a, 17b wit h accompanying loss of -COOH or -COOMe was observed, in preparatively usefu l yields. A mechanism is proposed for this interesting transformation.