Continuing these investigations, we have synthesized some 9-alkylamino-4-methoxy-7, 7- dimethyl-7, 8-dihydro-l, 3-diazaphenothiazines (la-h) by reacting enamines of 2-bromo-5, 5- dimathylcyclohexane-l, 3-dione (IVa-h) with 4-methoxy-5-amino-6-mercaptopyrimidine (V), and examined the effects of the structure of the alkyl group in the amino-group in the pharmacological properties of these compounds. r