Heterocyclic compounds as phosphodiesterase inhibitors

Compounds of the formula (I), their derivatives, analogs, tautomeric forms, regioisomers, stereoisomers, polymorphs, solvates, intermediates, pharmaceutically acceptable salts, pharmaceutical compositions, N-oxides, metabolites and prodrugs thereof. These compounds are phosphodiesterase type 4 (PDE4) inhibitors. They are useful in the treatment of a variety of allergic or inflammatory diseases including asthma, COPD, chronic bronchitis, atopic dermatitis, allergic rhinitis, allergic conjunctivitis, vernal conjuctivitis, psoriasis, rheumatoid arthritis, ulcerative colitis, Crohn's disease, uveitis, NASH and lupus.