Phenylurea, phenylthiourea, benzylcarbamate and toluenesulfonate of L-alanyl-L-proline(comp. $3{sim}6$) were synthesized and their effects against angiotensin-converting enzyme (ACE) were tested. Comp. 3 showed only mild inhibitory activities against ACE while comp. $4{sim}6$ were inert indicating that those functional groups were not suitable for interactions with ACE. Ortho-hydroxy- or ortho-carboxy-benzamide of proline (comp. 7) and phenylalanine (comp. 8 and 9) were also tested. Of the benzamides, ortho-hydroxy function was unsuitable to exert inhibitory activities against ACE. Ortho-carboxy group of 9 seemed to have mild interactions with active site of ACE possibly because of the shorter distance between the amide and ortho-carboxyl group of the compound than the corresponding two active sites of the enzyme.