Synthesis of New Functionalized 6/8-Methylindolizinecarboxylate Derivatives through 1,3-Dipolar Cycloaddition under Mild Conditions

T6/8-Substituted indolizines have been reported to act as calcium entry blockers, HIV-1 integrase/aromatase/phosphatase inhibitors. A library of new 6/8-methylindolizinecarboxylate derivatives has been obtained from regioselective 1,3-dipolar cycloaddition of unsymmetrically substituted pyridinium ylides and acetylene carboxylates. Substitution in the pyridine ring is not found to control the site of cycloaddition sterically. Unsymmetrical substitution in dipolarophile leads to completely regioselective cycloaddition with respect to the dipole. [GRAPHICS]