Approach to novel isotetronic acid derivatives: DBU-Et3N-mediated aldol/lactonization/O-protection sequence of 2-oxocarboxylic esters

An efficient synthesis of novel O-protected isotetronic acids is described.The method relies on DBU (1,8-diazabicyclo[5.4.0]-undec-7-ene) and triethylamine triggered homo-aldol reactions of 2-oxocarboxylic esters, followed by successful ring closure via lactonization and O-protection with various electrophiles.The unprotected isotetronic acids were also achieved with moderate to high yields if the free-OH group were pre-capped by the silylation agent TMSCl.All the three reaction steps were conducted in a sequential manner, without isolation of any intermediates.