Table 1.

Binding constants for 5 and 6 with deconstructed barbituric acid receptors 1a-f, 3a-c, and 4a-c.^a

	Binding Constant (Ka, M-1)			Binding Constant (Ka, M-1)
	5	6		5	6
1a	85 ± 25	490 ± 70	3a	70 ± 37b	Ka1 = 1230 ± 280b
					Ka2 = 184 ± 78b
1b	2 ± 1	3 ± 1	3b	40 ± 4	74 ± 15
				– b,c	7 ± 1b
1c	7 ± 2	21 ± 3	3c	– b,c	24 ± 7b
1d	17 ± 2	28 ± 2	4a	139 ± 18b	70 ± 9b
1e	29 ± 1	109 ± 14	4b	174 ± 3	40 ± 3
				6 ± 2b	7 ± 5b
1f	3 ± 1	6 ± 1	4c	4 ± 8b	22 ± 10b

^aTitrations were performed in CDCl₃ at 25 °C. All measurements are the average of at least three independent titrations.

^bPerformed in 5% DMSO in CDCl₃ due to poor solubility of either the host or the host-guest complex.

^cBinding constant too low (< 5 M^-1) to measure accurately.