1,3-Diazepinones. 2. The Correct Structure of Squamolone as 1-Carbamoyl-2-pyrrolidinone and Synthesis of Authentic Perhydro-1,3-diazepine-2,4-dione

Article abstract of DOI:10.1021/jo01314a018

The natural product squamolone,previously reported as 4-oxoperhydro-1,3-diazepin-2-one (1), was found to be instead 1-carbamoyl-2-pyrrolidinone (2).An unequivocal synthesis of the diazepinedione 1 starting from glutaric acid monoamide (6) produced the desired compound in five steps.Diborane reduction of 1 yielded the known perhydro-1,3-diazepin-2-one (10, tetramethyleneurea), confirming the seven-membered-ring structure of 1.A detailed analysis of the IR, NMR, and mass spectra of squamolone (2) and its isomer 1 is presented.A one-step synthesis of squamolone (2) starting with 4-aminobutyric acid 3 is reported.