Table 1.

Aldol Additions of 1c and Isobutyraldehyde in the Presence of Histidine Derivatives

entry	catalyst	Yield a	ee b
1		70%	77%
2		11%	48%
3		35%	37%
4		21%	12%
5		NR c	N/A

^aIsolated yield.

^bDetermined by ¹H NMR after derivatization of 2c to the Mosher's ester.

^cNo reaction.