INCORPORATION OF CONFORMATIONALLY CONSTRAINED PHENYLALANINE DERIVATIVES TIC, SIC, HIC AND NIC INTO A CHOLECYSTOKININ-B/GASTRIN RECEPTOR ANTAGONIST

A concise synthesis of (E)-3-aryl-2,3,4,5-tetrahydro-1H-3-benzazonines by aryne induced [2,3] Stevens rearrangement of 1,2,3,4-tetrahydroisoquinolines

(E)-3-Aryl-2,3,4,5-tetrahydro-1H-3-benzazonines were prepared in moderate to good yields with excellent diastereoselectivity via aryne induced [2,3] Stevens rearrangement.

Diversity-oriented synthesis of medicinally important 1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid (Tic) derivatives and higher analogs

1,2,3,4-Tetrahydroisoquinoline-3-carboxylic acid (Tic) is a constrained analog of phenylalanine (Phe). The Tic unit has been identified as a core structural element present in several peptide-based drugs and forms an integral part of various biologically active compounds. This report covers the biological significance of the Tic core and provides a detailed account of various synthetic approaches available for the construction of Tic derivatives. Along with the traditional methods such as the Pictet-Spengler and Bischler-Nepieralski reactions, we cover various recent approaches such as enyne metathesis, [2 + 2 + 2] cycloaddition and the Diels-Alder reaction to generate Tic derivatives. In addition, syntheses of higher analogs of Tic are also discussed.

Convenient synthesis of trans-beta-amino carboxylic esters with an azetidine skeleton via rearrangement of beta,gamma-aziridino alpha-amino esters

A short and facile approach to biologically interesting N-protected alkyl 3-aminoazetidine-2-carboxylic esters, a new class of conformationally restricted beta-amino esters, was developed. Reduction of anti-beta,gamma-aziridino-alpha-(N-diphenylmethylidene)amino esters and subsequent regioselective intramolecular ring opening of the beta,gamma-aziridine ring via nucleophilic attack of the alpha-amino function afforded the trans-azetidines.

CCK(2) receptor antagonists containing the conformationally constrained phenylalanine derivatives, including the new amino acid Xic

The conformationally constrained analogues of phenylalanine, tetrahydroisoquinoline-3-carboxylic acid (Tic), Sic, Hic and Nic, and the new amino acid Xic have been incorporated into a potent and highly selective cholecystokinin-2 (CCK(2)) receptor antagonist (2) in place of the phenylalanine residue, producing compounds 15a-e. High selectivities for CCK(2) over CCK(1) were observed for compounds 15a-e. The in vitro profile of the analogue containing the Nic residue (15d) was identical to that of compound 2, whereas the alternative conformational constraints resulted in a significant loss of affinity. The apparent advantage of Nic in the context of these CCK(2) ligands was subsequently demonstrated to be statistically significant.

Synthesis and structural analysis of dehydrophenylalanine cyclophanes

The syntheses and structures of three cyclophanes containing two (Z)-dehydrophenylalanine residues are reported; the length of the tethers between the two amino acid residues is easily altered and changing this parameter has a significant effect on the solid state structures of the cyclophanes.

Benzotriazonine as a new core structure for the design of CCK-receptor antagonists

The search for heterocyclic scaffolds for the design of non-peptidic and highly selective agonists or antagonists of peptide hormone receptors led to 4-N-benzyl-2,3,4,5,6,7-hexahydro-1H-1,4,7-benzotriazonin-2, 6-dione with a 9-membered core structure as a new low mass lead compound that exhibits submicromolar antagonistic activity at the CCK-A receptor with a 54-fold selectivity over the CCK-B/gastrin receptor.