合成路线1

Acid hydrolysis of the acetamido group of (V) gave amino acid (XI), which was further esterified with HCl in MeOH. The resulting amino ester (XII) was then protected as the tert-butyl carbamate (XIII) and the methyl ester was hydrolyzed to carboxylic acid (XIV) by means of LiOH. Coupling of (XIV) with 3-aminopropionitrile (XV) using BOP reagent provided the N-cyanoethyl amide (XVI). Elaboration of the tetrazole ring (XVII) was carried out by treatment of (XVI) with trimethylsilyl azide, diisopropyl azodicarboxylate and triphenyl phosphine. The Boc group of (XVII) was then deprotected by treatment with formic acid. The resulting amine (XVIII) was condensed with formaldehyde, followed by reaction of the intermediate trimeric hexahydrotriazine with diphenyl phosphite to furnish alpha-aminophosphonate (XIX). Basic cleavage of the cyanoethyl group of (XIX) produced the N-dealkylated tetrazole (XX). Finally, basic hydrolysis of phosphonate ester groups of (XX) gave rise to the title compound.