Table 1. Optimization of Regioselective Acylation of 10.

entrya	base	temp (°C)	solvent (V)	LCAPb,c
				8	10	11	12
1	Et3N	19	10	59	0	17	0.5
2	Bu3N	19	10	52.6	0	21.6	1.1
3	DIPEA	19	10	60.4	0	17.5	0
4	lutidine	19	10	34.5	0	30.2	6.5
5	DBU	19	10	93.5	0.2	6.1	0.1
6	DBU	19	2.5	89.3	7.1	3.6	0.3
7	DBU	19	5	89.4	5.3	4.3	0.3
8	DBU	19	7	92.5	0.4	6.1	0.1
9	DBU	0	10	94.7	2.2	2.1	0.6
10	DBU	40	10	88.7	6	4.6	0.4
11	DBU	56	10	85.5	8.5	5.4	0.6

^aReaction conditions: isobutyric anhydride (1.1 equiv), base (2.1 equiv), DMAP (20 mol %), and CH₃CN.

^bReaction time: 8 h for entries 1–4 and 3 h for entries 5–11.

^cLCAP at 260 nm.