Direct electrophilic fluorination of tyrosine in dermorphin analogues and its effect on biological activity, receptor affinity and selectivity.
In a preliminary communication we reported [(Tetrahedron Lett. 31, 619 (1990)] that acetyl hypofluorite can be used efficiently to introduce fluorine regiospecifically (ortho to OH) into the phenolic ring of tyrosine-containing peptides. This procedure has been applied to the fluorination of a number of mu-selective opioid peptides derived from dermorphin. While the procedure can be used even when the side chains of Arg, Lys, and Tyr are left unprotected, the sulfoxide of a Met(O)-containing analogue was oxidized to sulfone faster than fluorination of the phenolic ring. This method can also be used when the peptide is attached to Merrifield resin. Thus, Tyr(3-F)-D-Ala-Phe-Gly-NH2 and Tyr(3-F)-D-Arg-Phe-Lys-NH2 (F-DALDA) have been prepared, purified, and characterized. Affinities of these fluorinated peptides for both mu- and delta- opioid receptors are reduced (two- to nine-fold) relative to their nonfluorinated analogues, but their selectivity for mu-opioid receptors is not significantly altered. Similarly, the in vitro biological potencies (GPI and MVD assays) of the fluorinated analogues are reduced (two- to seven-fold) relative to their nonfluorinated parent peptides. Thus, F-DALDA, which has high affinity (Ki mu = 15.2 nM) and selectivity (Ki delta/Ki mu = 5390) for mu-opioid receptors, has potential use in biochemical studies which utilize 19F or 18F- labeled compounds.
Labroo
V M
VM
Laboratory of Bioorganic Chemistry, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD.
Hebel
D
D
Kirk
K L
KL
Cohen
L A
LA
Lemieux
C
C
Schiller
P W
PW
D000595:Amino Acid Sequence; D000701:Analgesics, Opioid / Q000138:chemical synthesis* / Q000378:metabolism; D000818:Animals; D001921:Brain / Q000378:metabolism; D005461:Fluorine / Q000378:metabolism*; D008969:Molecular Sequence Data; D009842:Oligopeptides / Q000138:chemical synthesis* / Q000378:metabolism; D018847:Opioid Peptides; D051381:Rats; D011957:Receptors, Opioid / Q000378:metabolism; D017465:Receptors, Opioid, delta; D017450:Receptors, Opioid, mu; D014443:Tyrosine / Q000378:metabolism
D000701:Analgesics, Opioid; D009842:Oligopeptides; D018847:Opioid Peptides; D011957:Receptors, Opioid; D017465:Receptors, Opioid, delta; D017450:Receptors, Opioid, mu; D005461:Fluorine; C030058:dermorphin; D014443:Tyrosine