Isoniazid SAR and Synthesis Medicinal Chemistry III

Pyridine ring is essential for activity. Substitution at R-1, R-2,  causes Variable activity.

any Substitution at  R-3 position causes loss of activity .

If  Pyridine Ring is replaced by piperidine ring causes less active compound.

addition of iso-propyl group at R-2 Position Causes loss of Anti-tubercular activity.