Table 2.

Substituent for compounds 15–21

Compounds	X	R1′	R2′	R3′	R4′	R5′	R6′	R7′	R8′
15	C	OH	H	OH	H	H	H	OH	H
16	C	OH	H	OH	H	H	OH	H	OH
17	C	OH	H	OH	H	OH	H	H	OH
18	N	H	H	OH	OH	H	OH	H	OH
19	N	H	H	OH	OH	OH	H	H	OH
20	N	H	CH3	OH	CH3	H	OH	H	OH
21	N	H	CH3	OH	CH3	OH	H	H	OH