Table 2.

HPLC-RI low population structure features

Feature	Counta	%b	IGroupc
aldehyde	3	0.8%	aliphatic O
diazole	12	3.0%	pyridine, pyrrole
purine	12	3.0%	pyridine, aniline, pyrrole
guanadine	6	1.5%	aliphatic N
pyrimidine	4	1.0%	pyridine, aniline
diphenylamine	1	0.3%	pyrrole
carbamate	8	2.0%	amide, aliphatic O
oxime	1	0.3%	aliphatic N, aliphatic O
guanine	9	2.3%	amide, pyridine, pyrrole
xanthine	9	2.3%	amide, pyridine, pyrrole
cytosine	8	2.0%	amide
uracil	6	1.5%	amide
urea	6	1.5%	amide
barbiturate	4	1.0%	amide
uric acid	4	1.0%	amide
imide	3	0.8%	amide
hydantoin	3	0.8%	amide
flavin	2	0.5%	amide
pyrazolidinone	2	0.5%	amide
phosphate	16	4.0%	acid O
sulfonic acid	7	1.8%	acid O
sulfinic acid	1	0.3%	acid O
phosphonate	1	0.3%	acid O
thioether	9	2.3%	aliphatic S
thioanisole	6	1.5%	aliphatic S
disulfide	3	0.8%	aliphatic S
sulfoxide	1	0.3%	aliphatic S, aliphatic O
vinyl	13	3.3%	acidic CH
quaternary N+	9	2.3%	protonated N
pyridinium N+	5	1.3%	protonated N
thiazole	3	0.8%	aromatic S, pyridine
thiophene	2	0.5%	aromatic S

^aCount of compounds with at least one example of the feature.

^bPercent of compounds with at least one example of the feature.

^cIGroup descriptor or descriptors where structure information for atoms in the group was assigned.