Synthetic routes to the Neuropeptide Y Y1 receptor antagonist 1229U91 and related analogues for SAR studies and cell-based imaging

Abstract

The potent Y1 receptor antagonist, 1229U91 has an unusual cyclic dimer structure that makes syntheses of analogue series quite challenging. We have examined three new routes to the synthesis of such peptides that has given access to novel structural variants including heterodimeric compounds, ring size variants and labelled conjugates. These compounds, including a fluorescently labelled analogue VIII show potent antagonism that can be utilised in studying Y1 receptor pharmacology.

Heterodimeric Analogues of the Potent Y1R Antagonist 1229U91, Lacking One of the Pharmacophoric C-Terminal Structures, Retain Potent Y1R Affinity and Show Improved Selectivity over Y4R

“…However, 11a , 11b , and 11c all showed 10–30-fold reduced Y 1 R affinity compared to 1229U91 itself, with an equivalent decrease in their effects as antagonists (Figure B). The relatively reduced affinity of 11c , compared to 1229U91 under these conditions is in contrast to our previously published data using a radioligand receptor binding assay against membrane homogenates from Y 2 R/Y 4 R knockout mice and recombinant cells . As noted in our previous studies, better alignment of whole cell competition binding using fluorescent ligands and functional readouts are observed and to be expected, compared to radiolabeled agonist experiments in membrane homogenates …”

“…The ring size variants of 1229U91, compounds 11a , 11b , and 11c all showed high affinity for Y 1 R with K i values in the nanomolar range (Table ) and were nonsurmountable antagonists of NPY-induced β-arrestin2 recruitment as we have previously observed for other 1229U91 analogues (Figure A) . However, 11a , 11b , and 11c all showed 10–30-fold reduced Y 1 R affinity compared to 1229U91 itself, with an equivalent decrease in their effects as antagonists (Figure B).…”

“…We pursued the solution phase formation of cyclic dimers via an orthogonal protection strategy described previously to create a series of ring-size variant and alanine scanning modifications. The strategy is summarized for the ring size variants as shown in Scheme …”

“…We previously described the development of an unambiguous synthesis of cyclic dimers that avoids concomitant competing intramolecular cyclization and allows the preparation of heterodimeric structures . In an attempt to understand which of the above mechanisms governs the potent antagonism of Y 1 R by 1229U91, we have explored variation of ring cycle size within 1229U91 and conducted the first residue-by-residue interrogation within a single dimer arm.…”

Optically Pure, Structural, and Fluorescent Analogues of a Dimeric Y4 Receptor Agonist Derived by an Olefin Metathesis Approach

“…[6][7][8][9] In developing such ligands, truncated peptide analogues are becoming increasingly popular. For example, [Nle 30 ]hPP [25][26][27][28][29][30][31][32][33][34][35][36] and [Leu 34 ]pNPY [25][26][27][28][29][30][31][32][33][34][35][36] were found to be Y 4 R selective partial agonists, 10 and a nonapeptide based on the C-terminal fragment of NPY, Ile-Asn-Pro-Ile-Tyr-Arg-Leu-Arg- [28][29][30][31][32][33][34][35][36] ], also known as 1229U91, showed enhanced potency at both receptor subtypes but is in particular the most potent known Y 1 R antagonist. [13][14][15][16][17] Another of several highly potent Y receptor ligands based upon dimeric C-terminal sequences is D/L-2,7-diaminooctanedioyl-bis(YRLRY-NH 2 ), 1 (BVD-74D) 18 ( …”