[Structure activity relation study of matrine-type alkaloids. Part III].

6-Acyldecahydro [1,6]naphthyridines were synthesized as derivatives of matrine-type and allomatrine-type alkaloids, and the structure-activity relations were examined by the acetic acid-induced abdominal contraction test. All synthesized derivatives produced the antinociception in mice. The antinociceptive potencies of 15a-c and 16a-c were lower than those of 17a-c, 18a-c, 19a-c and 20a-c. Furthermore, those of the matrine-type derivatives 17b and 17c are greater than other derivatives. These findings suggest that less hindered tertiary amine and highly lipophilic acyl group are better functional groups for the greater antinociceptive potencies. Furthermore, these findings suggest that A or B ring of 1 and 2 are not essential for the antinociceptive effect.