PYRAN AND 1,3-DIOXANE DERIVATIVES

摘要

A compound of the formula : wherein R<1> is hydrogen or lower alkyl, R<2> is carboxy(lower)alkyl or protected carboxy(lower)alkyl and R<3> is -CH2NH-R<4>, -CH=N-R<4> or -CH2-R<5> in which R<4> is acyl, acylamino, heterocyclic amino, heterocyclic(lower)alkyl or ar(lower)alkoxy and R<5> is acyloxy or heterocyclic(lower)alkoxy and X is -O- or -CH2-, or pharmaceutically acceptable salt thereof, processes for their preparation and pharmaceutical compositions comprising them as an active ingredient.