合成路线1

The selective silylation of azetidine (I) with TBDMSCl and Et3N in CH2Cl2 gives the fully silylated azetidine (II), which is condensed with 1-(trimethylsilyloxy) cyclohexene (III) by means of SnCl4 in CH3CN to yield the adduct (IV). The N-silylation of (IV) with TBDMSCl and Et3N in DMF affords the disilylated compound (V), which is condensed with diethyl chlorophosphate by means of LiHMDS in THF providing the phosphate ester (VI). The reaction of (VI) with MCPBA in CH2Cl2 gives the epoxide (VII), which is treated with methylamine and K2CO3 in ethyl acetate to yield the secondary amine (VIII). The acylation of (VIII) with allyl chloroformate (IX) and Et3N in CH2Cl2 affords the carbamate (X), which is cyclized with allyl chlorooxalate (XI) and Et3N in CH2Cl2 providing the tricyclic compound (XII). The desilylation of (XII) with TBAF and HOAc in THF gives the hydroxy diallyl ester (XIII), which is treated with Pd(PPh3)4 and 5,5-dimethylcyclohexane-1,3-dione (DMCHE) to yield the tricyclic aminoacid (XIV). Finally this compound is treated with benzyloxy formimidate (XV) in a pH 8 buffer to afford the target N-methylformamidino compound.