合成路线1

Condensation of 2-formylcycloheptanone (I) with ethyl 3-aminocrotonate (II) provides ethyl carboxylate (III), which is then converted into carbonylguanidine (VI) by reaction with free guanidine (V) (obtained from guanidine hydrochloride (IV) by treatment with Na/MeOH) in refluxing isopropanol. Alternatively, carbonylguanidine (VI) can also be obtained by saponification of ethyl ester (III) with refluxing NaOH to yield carboxylic acid (VII), which is then activated with oxalyl chloride (A) in CH2Cl2 or with CDI in THF to allow condensation with guanidine (V) in THF. Finally, the corresponding maleate can be obtained by reaction of carbonylguanidine (VI) with maleic acid (VIII) in MeOH.