Table I.

Chemical structure of 1,3,7-substituted alkylxanthines

No.	Compound name	Radical 1	Radical 3	Radical 7
1	Xanthine	H	H	H
2	1-Methylxanthine	Me	H	H
3	3-Methylxanthine	H	Me	H
4	7-Methylxanthine	H	H	Me
5	1,3-Dimethylxanthine (theophylline)	Me	Me	H
6	1,7-Dimethylxanthine (paraxanthine)	Me	H	Me
7	3,7-Dimethylxanthine (theobromine)	H	Me	Me
8	1,3,7-Trimethylxanthine (caffeine)	Me	Me	Me
9	1-Ethylxanthine (Xt 101)	Et	H	H
10	3-Ethylxanthine (NY 457)	H	Et	H
11	1-Ethyl-3-methylxanthine (Xt 054)	Et	Me	H
12	1,3-Ethylxanthine (Xt 023)	Et	Et	H
13	1-Propylxanthine (Xt 102)	n-Pro	H	H
14	3-Propylxanthine (enprofylline)	H	n-Pro	H
15	1-Propyl-3-methylxanthine (Xt 055)	n-Pro	Me	H
16	3-Propyl-7-methylxanthine (Xt 016)	H	n-Pro	Me
17	1,7-Dimethyl-3-propylxanthine (Xt 017)	Me	n-Pro	Me
18	1-Propyl-3-ethylxanthine (Xt 059)	n-Pro	Et	H
19	1-Ethyl-3-propylxanthine (Xt 015)	Et	n-Pro	H
20	3-Propyl-7-ethylxanthine (Xt 018)	H	n-Pro	Et
21	1-Methyl-3-propyl-7-ethylxanthine (Xt 074)	Me	n-Pro	Et
22	1-Ethyl-3-propyl-7-methylxanthine (Xt 071)	Et	n-Pro	Me
23	1,3-Dipropylxanthine (Xt 043)	n-Pro	n-Pro	H
24	3,7-Dipropylxanthine (Xt 019)	H	n-Pro	n-Pro
25	1,3-Dipropylxanthine (Xt 072)	n-Pro	n-Pro	Me
26	1-Methyl-3,7-dipropylxanthine (Xt 075)	Me	n-Pro	n-Pro
27	1-Butylxanthine (Xt 103)	n-Bu	H	H
28	3-Butylxanthine (NY 466)	H	n-Bu	H
29	1-Butyl-3-methylxanthine (Xt 056)	n-Bu	Me	H
30	1-Methyl-3-butylxanthine (Xt 011)	Me	n-Bu	H
31	1-Butyl-3-ethylxanthine (Xt 060)	n-Bu	Et	H
32	1-Ethyl-3-butylxanthine (Xt 031)	Et	n-Bu	H
33	1-Propyl-3-butylxanthine (Xt 047)	n-Pro	n-Bu	H
34	1-Butyl-3-propyl-7-methylxanthine (Xt 073)	n-Bu	n-Pro	Me
35	1-Methyl-3-propyl-7-butylxanthine (Xt 077)	Me	n-Pro	n-Bu
36	1,3-Dibutylxanthine (Xt 048)	n-Bu	n-Bu	H
37	1-Pentylxanthine (Xt 104)	n-Pent	H	H
38	1-Pentyl-3-methylxanthine (Xt 057)	n-Pent	Me	H
39	1-Pentyl-3-ethylxanthine (Xt 061)	n-Pent	Et	H
40	1-Ethyl-3-pentylxanthine (Xt 066)	Et	n-Pent	H
41	1-Pentyl-3-propyl-7-methylxanthine (Xt 078)	n-Pent	n-Pro	Me
42	1-Pentyl-3-butylxanthine (Xt 049)	n-Pent	n-Bu	H
43	1-Hexylxanthine (Xt 105)	n-Hex	H	H
44	3-Hexylxanthine (Xt 040)	H	n-Hex	H
45	1-Hexyl-3-methylxanthine (Xt 058)	n-Hex	Me	H
46	1-Methyl-3-hexylxanthine (Xt 069)	Me	n-Hex	H
47	1-Hexyl-3-ethylxanthine (Xt 062)	n-Hex	Et	H
48	1-Ethyl-3-hexylxanthine (Xt 070)	Et	n-Hex	H
49	1-Hexyl-3-propyl-7-methylxanthine (Xt 079)	n-Hex	n-Pro	Me
50	1-Hexyl-3-butylxanthine (Xt 050)	n-Hex	n-Bu	H

Each compound tested is listed in the first column. The compounds are placed in order of increasing number of carbons from radical 1 to radical 7. The columns labeled group 1, 3 or 7 are based on the structure shown in Figure 1 and indicate hydrogen (H), methyl (Me), ethyl (Et), propyl (n-Pro), butyl (n-Bu), pentyl (n-Pent) and hexyl (n-Hex).