The present invention relates to heterocyclic compounds of Formula (1), in all their stereoisomeric and tautomeric forms； and their pharmaceutically acceptable salts, solvates, polymorphs, prodrugs, carboxylic acid isosteres and N-oxides. The invention also relates to processes for the manufacture of the heterocyclic compounds and to pharmaceutical compositions containing them. The said compounds and their pharmaceutical compositions are useful in the prevention and treatment of diseases or disorders mediated by diacylglycerol acyltransferase (DGAT), particularly DGAT1. The present invention further provides a method of treatment of such diseases or disorders by administering a therapeutically effective amount of said compounds or their pharmaceutical compositions, to a mammal in need thereof.
