2^′, 6^′-Dimethylphenylalanine : A Useful Aromatic Amino Acid Surrogate for Tyr or Phe Residue in Opioid Peptides

Table 7

Comparison of stability of Dmp-containing peptides toward enzymatic degradation.

Peptides	Half-life time (min)^a
	Aminopeptidase M	Rat brain homogenate
DYN(I-13)-NH2	15.5	435
[Dmp^4]DYN(l-13)-NH2 (26)	NT^b	315
[Dmp^1]DYN(1-13)-NH2 (27)	>30	577
[Dmp^1,4]DYN(1-13)-NH2 (28)	NT^b	770
NOC(1-13)-NH2	12	41.5
[Dmp^4]NOC(1-13)-NH2 (29)	NT^b	33.6
[Dmp^1]NOC(1-13)-NH2 (30)	28	60.3
[Dmp^1,4]NOC(l-13)-NH2 (31)	NT^b	27.1
Met-enkephalin	<5	8.5

^aDetermined by HPLC. ^bNot tested.