Table 2. Purification of 11:12 Monoamide Mixture^a.

				HILIC (A % ratio)b
entry	acid	solvent	result	11′:12′
1	4.0 M HCl	1,4-dioxane	amide cleaved	ND
2	1.2 M HCl	IPA	amide cleaved	ND
3	H2SO4	EtOH	amide cleaved	ND
4	H3PO4	EtOH	no precipitate	NA
5	formic acid	EtOH	no precipitate	NA
6	benzoic acid	EtOH	no precipitate	NA
7	citric acid	EtOH	no precipitate	NA
8	d-(−)-tartaric acid	EtOH	no precipitate	NA
9c	l-(+)-tartaric acid	EtOH	stable white salt	25:1
10	l-(+)-tartaric acid	Methanol	no precipitate	NA
11	l-(+)-tartaric acid	Acetone	no precipitate	NA
12	l-(+)-tartaric acid	EtOAc	no precipitate	NA
13d	l-(+)-tartaric acid	i-PrOH	hygroscopic white salt	98:2
14d	l-(+)-tartaric acid	i-PrOH/MeOH (9:1)	stable white salt	100:0

^aAll of the reactions were carried out with ∼9:1 regioisomeric mixture of 11:12 (1.0 g, 1.0 equiv), acid (1.0 equiv), solvent (10 V), rt, 3h.

^bHILIC ratio at 210 nm. ND = Not determined. NA = Not applicable.

^c80% of mass recovery.

^d78% of isolated yield.