Synthesis of α‐amino phosphonic acids via oxoiminium salts

Abstract

Abstract The oxoiminium salts 4a, b , and 8 obtained by alkylation with Et 3 OBF 4 of the aldonitrones 3a, b , and 7 react with diphenyl hydrogen phosphite to give the N ‐alkoxy α‐amino phosphonic esters 6 and 9a, b . Similarly, the cyclic imine oxides 10a, b and the cyclic oxime ethers 14a, b afford the α‐branched N ‐alkoxy α‐amino phosphonic esters 12a, b and 16a, b , respectively. Hydrogenolysis and ester hydrolysis affords the α‐methyl α‐amino phosphonic acid hydrochlorides 13a, b and 17a, b .