(S)-5-(5-amino-2-pyrazinyl)-2-[[(1,1-dimethylethoxy)carbonyl]amino]-pentanoic acid 、
4-(difluoromethylidene)piperidine hydrochloride 以to give 2.61 g of 1,1-dimethylethyl (S)-[4-(5-amino-2-pyrazinyl)-1-[[4-(difluoromethylene)piperid-1-yl)carbonyl]butyl]carbamate in the form of an amorphous powder的产率得到1,1-dimethylethyl (S)-[4-(5-amino-2-pyrazinyl)-1-[[4-(difluoromethylene)piperid-1-yl)-carbonyl]butyl]carbamate