Table 6. Molecular geometry (Å, °) of N1-substituted isocytosine.

	REFMAC	CSD†	QM for iC	QM for iCiG‡
N1—C2	1.410	1.352 (3)	1.380	1.385
C2—N3	1.350	1.332 (2)	1.295	1.324
N3—C4	1.350	1.364 (2)	1.393	1.375
C4—C5	1.390	1.445 (3)	1.467	1.461
C5—C6	1.390	1.340 (3)	1.338	1.350
C6—N1	1.337	1.357 (3)	1.383	1.382
C2—N2	1.355	1.324 (3)	1.363	1.340
C4—O4	1.250	1.247 (2)	1.220	1.244
C6—N1—C2	120.0	120.23 (16)	117.05	118.2
N1—C2—N3	120.0	122.00 (18)	124.67	122.2
C2—N3—C4	120.0	119.65 (16)	120.86	121.7
N3—C4—C5	120.0	118.94 (15)	115.97	117.3
C4—C5—C6	120.0	118.40 (20)	120.10	119.0
C5—C6—N1	120.0	120.77 (18)	121.35	121.7
N2—C2—N1	120.0	118.74 (16)	116.78	118.8
N2—C2—N3	120.0	119.24 (18)	118.55	119.0
O4—C4—C5	120.0	121.69 (17)	122.29	121.9
O4—C4—N3	120.0	119.35 (17)	121.75	120.8
RMSD versus QM for iC (d/a)				0.0176/1.294

^†ICYTIN01; N1-protonation.

^‡Suggested standard deviations 0.009 Å for bonds, 0.7° for angles.