摘要 |
<p>A compound of the formula : <CHEM> wherein R<1> is lower alkyl optionally substituted with a substituent selected from the group consisting of acyl,hydroxy, lower alkoxy, aryl, lower alkylthio and a group of the formula : <CHEM> in which R<5> is hydrogen or acyl and R<6> is hydrogen or lower alkyl; aryl; or amino optionally substituted with substituent(s) selected from the group consisting of lower alkyl and acyl; and R<2> is hydrogen or lower alkyl; or R<1> and R<2> are taken together with the attached nitrogen atom to form a heterocyclic group optionally substituted with substituent(s) selected from the group consisting of lower alkyl, hydroxy(lower)alkyl, lower alkoxy(lower)alkyl, acyl(lower)alkyl, oxo and acyl; R<3> is hydrogen or lower alkyl; and R<4> is lower alkyl; and its pharmaceutically acceptable salt, processes for the preparation thereof and pharmaceutical composition comprising the same.</p> |