Table 3.

Addition reactions of tyrosine-containing peptides to imines 1 and 11.^a

entry	imine	peptide	reaction pH	yieldb (%)
1	1	GlyTyr	pH 5	25c (54)d [133]e
2	1	GlyTyr	pH 7	34c (38)d [110]e
3	1	GlyTyr	pH 8.5	[91]e
4	1	AlaTyrAla	pH 7	[109]e
5	11	GlyTyr	pH 7	[91]e
6	11	AlaTyrAla	pH 7	[74]e [99]e,f
7g	11	AlaTyrAla	pH 6	[58]e [96]e,f

^aConditions: Imine (50 mM) and peptide (10 mM) in 100 mM NaH₂PO₄-Na₂HPO₄ (pH 7), 100 mM NaH₂PO₄ (for pH 5), or 100 mM Na₂HPO₄ (for pH 8.5) prepared with D₂O at 37 °C for 24 h.

^bDetermined by ¹H NMR of the reaction mixture.

^cMono-addition product.

^dDi-addition product (di-addition at tyrosine).

^ePercentage of modified ortho positions of the tyrosine phenolic OH; complete conversion to the di-addition product = 200%.

^fData after 48 h.

^gReaction in D₂O.