N-Methyl-N-phenyl-5-oxa-1-azaspiro[2.5]oct-1-en-2-amine — Synthesis and Reactions of a Synthon for an Unknown α-Amino Acid

The synthesis of the heterospirocyclic amino azirine N-methyl-N-phenyl-5-oxa-1-azaspiro[2.5]oct-1-en-2-amine (6a) was achieved from 3,4-dihydro-2H-pyrane (7) via N-methyl-N-phenyltetrahydropyran- 3-thiocarboxamide (11). The reactions of 6a with thiobenzoic acid and Z-Phe-OH, respectively, leading to the corresponding 3-benzoylaminotetrahydropyran- 3-thiocarboxamide (13) and the diastereoisomeric dipeptide amides (14), respectively, demonstrate that 6a is a valuable synthon for the hitherto unknown 3-aminotetrahydropyrane-3-carboxylic acid. The structure of 13 was established by X-Ray crystallography