Table 1.

Structures of betulin derivatives screened against BoNT/A protease

Compound	R1	R2	R3
1	OH	CH2OH
2	OH	CH2OH
3	OH
4	OH
5	OH
6	OH
7	OH
8	OH
9	OH	OAc
10	OAc	OH
11	OAc	CH2OAc
12	OAc	CH2OAc
13 2	OAc	CH2OAc
14 2	OAc	CH2OAc
15	OAc
16	OAc
17
18	OH	CO2H
19	OH	CO2Me
20	O=	CHO
21	O=	CO2H
22	O=	CO2Me
23	O=	CO2H
24	O=
25	O=
26	O=
27	OH	CH=NOH
28	=NOH	CH=NOH

Compound	R3	R4
29	Me	Ac
30	Me	CocHex
31	Me	COPh
32	n-Bu	Ac
33	Ph	Ac
34	Bn	Ac
35	3-MeO-Ph	Ac
36	4-F-Ph	Ac
37	3-NO2-Ph	Ac
38	4-Ac-Ph	Ac
39	4-Cl-Ph	Ac
40	indan-5-yl	Ac