Transformation of 5-Hydroxy-to ( 5-Chloropentanoyl ) amino Derivatives under ‘ Direct Amide Cyclization ’ Conditions

The application of the ‘direct amide cyclization’ conditions to the linear delta-hydroxy diamide 11 is described (Scheme 3). Instead of the cyclization to the expected nine-membered cyclodepsipeptide, only the chloro acid 12 was obtained. Its formation could be explained by consecutive formation of the 1,3-oxazol-5(4H)-one 16 and the six-membered imino… CONTINUE READING