A Novel Traceless Resin-Bound Guanidinylating Reagent for Secondary Amines To Prepare N,N-Disubstituted Guanidines

On the search of new I2-IBS aliphatic ligands: Bis-guanidino carbonyl derivatives

Continuing with our search of aliphatic dicationic derivatives as I2-IBS ligands and looking at Amiloride, a known ligand of I2-IBS, we have incorporated the guanidinocarbonyl moiety into our aliphatic compounds with the intention of improving the binding to I2-IBS. Thus, we present the different approaches to the preparation and pharmacological evaluation (in human brain tissue) as I2-IBS ligands of a new series of aliphatic derivatives incorporating the guanidinocarbonyl group and with different chain length (n= 8-12, and 14 methylene groups).

Concise synthesis of guanidine-containing heterocycles using the Biginelli reaction

Two general methods for the synthesis of 2-imino-5-carboxy-3,4-dihydropyrimidines were developed using the three-component Biginelli reaction. The first method utilizes pyrazole carboxamidine, a beta-ketoester, and an aldehyde in an initial Biginelli reaction. After Boc protection, these products undergo aminolysis and acidic deprotection to generate 2-imino-5-carboxy-3,4-dihydropyrimidines in a four-step sequence. The second method utilizes a triazone-protected guanidine, a beta-ketoester, and an aldehyde in a Biginelli reaction. Acidic cleavage of the triazone yields 2-imino-5-carboxy-3,4-dihydropyrimidines in a two-step sequence. We also describe the further elaboration of several of these products using a tethered Biginelli reaction to give triazaacenaphthalene structures similar to those found in crambescidin and batzelladine alkaloids.

Amino Acid Binding by 2-(Guanidiniocarbonyl)pyridines in Aqueous Solvents: A Comparative Binding Study Correlating Complex Stability with Stereoelectronic Factors

A series of guanidiniocarbonylpyridine receptors has been synthesized, and these compounds bind amino acids (carboxylate forms) in aqueous DMSO with association constants ranging from K = 30 to 460 M(-1) as determined by NMR titration experiments. The differences in the complex stabilities can be correlated with steric and electrostatic effects with the aid of calculated complex structures. For example, the electrostatic repulsion between the pyridine nitrogen lone pair and the bound carboxylate makes anion binding less efficient than with the analogous pyrrole receptors previously introduced by us for carboxylate binding in water. Furthermore, steric interactions between the receptor side chain as in 2 b and the bound substrate also disfavor complexation.

New reagents, reactions, and peptidomimetics for drug design

It has been a major focus in our laboratories to prepare novel reagents and peptidomimetic structures for drug design. We have designed and prepared novel guanidinylation reagents that can be employed in solution or as solid phase reagents. We and others have utilized the reagent 3-(diethoxyphosphoryloxy)-1,2,3-benzotriazin-4(3H)-one (DEPBT) for amide bond formation to couple sterically hindered structures. These couplings proceed with remarkably strong resistance to racemization. In the area of peptidomimetics, we have incorporated novel building blocks to create biologically active compounds. These building blocks include thioether and alkylamine bridges, beta-methylated, and beta,beta-dimethylated amino acid residues. These mimetic structures have been incorporated into specific target molecules such as opioids to obtain cyclic peptidomimetics with potent and selective biological activity.