3, 4 R 'R2 R3 a H CH3 CH 3 b H CZH5 CH 3 c 0 CH 3 CH3 CH3 d m-CH3 CH3 CH3 e [2 CH3 CH 3 CH3 f m-CH3—(CH3) 3—gp CH3—(CHZ) 3—h m-OCH3 CH3 3 i 0-Cl CH3 CH3 j m-Cl CH 3 CH3 k 12 Cl CH3 CH 3 l m-Cl—(CHZ) 5—mp Cl—(CH2) 3~ n m-(n-C31-19S) CH3 C 3 0 p-(n—C4H., S) CH3 CH3