Table 1. Inhibitory Potency of 7 and 8 in Comparison to 9, MG-132, bortezomib, and carfilzomib.

	Ki in nM
	20S proteasome
inhibitor	CL-activitya	TL-activitya	PGPH-activitya	chymotrypsina	cathepsin Ba	m-calpaina
7	241 ± 62.2	8,040	N.I.b	N.I.b	3047 ± 1	2028 ± 319
8	54.5 ± 4.9	N.I.b	N.I.b	N.I.b	30345 ± 900	2983 ± 621
9	28.0 ± 9.9	N.T.c	N.T.c	N.I.b	2285 ± 1,700	1708 ± 99
MG-132	63.5 ± 21.5	N.I.b	3700	N.I.b	230 ± 206	653 ± 211
bortezomib	24.0 ± 2.8	N.T.c	N.T.c	N.I.c	N.I.c	N.I.c
carfilzomib	25.5 ± 12.0	N.T.c	N.T.c	N.I.c	N.I.c	N.I.c

^aAssay protocols are provided in the Supporting Information.

^bNo inhibition at 100 μM inhibitor concentration.

^cNot tested.