Table 2.

Activity of 1-Z-Azf-Ala-NR¹R² derivatives against human cytomegalovirus (HCMV)

Compd	R1, R2	EC50 (μM)	Cytotoxicity (μM)
		HCMVa	MCCb	CC50c
(S,S)-4a	H, C(CH)3	45	>100	>100
(R,S)-4a	H, C(CH)3	49	>100	>100
(S,S)-4b	H, CH2Ph	>20	100	42
(R,S)-4b	H, CH2Ph	>4	⩾20	42
(S,S)-4c	H, CH2CH(CH3)2	63	>100	>100
(R,S)-4c	H, CH2CH(CH3)2	>100	>100	>100
(S,S)-4d	H, Chx	>100	>100	>100
(R,S)-4d	H, Chx	>20	100	46
(S,S)-4e	CH3, CH3	>100	>100	>100
(R,S)-4e	CH3, CH3	>100	>100	>100
(S,S)-1	H, H	32	>50	50
11	Z-Phe-Ala-NH2	>100	>100	>100
12	Z-Phe-Ala-NHtBu	>100	>100	>100
GCV		7.0	⩾1575	580

^aEffective concentration required to reduce virus plaque formation by 50% (Davis strain). Virus input was 100 plaque forming units (PFU).

^bMinimum cytotoxic concentration that causes a microscopically detectable alteration of cell morphology.

^cCytotoxic concentration required to reduce cell growth by 50%.