Synthesis of Chiral β3-Aminoxy Peptides

Three Component Synthesis of β‑Aminoxy Amides

A multicomponent reaction for the synthesis of β‑aminoxy amides is described. In this reaction, N-hydroxamic acids, yna-mides and aldehydes could assemble efficiently to deliver structurally diverse β‑aminoxy amides under the...

A ring-closing metathesis-based approach to the synthesis of (+)-tetrabenazine

A modular stereoselective synthesis of the vesicular monoamine transport inhibitors (+)-tetrabenazine ((+)-1) and (+)-α-dihydrotetrabenazine ((+)-2) has been developed. The approach is based on amine 4 and acid 5 as the key building blocks, which were elaborated into macrolactam 3 by amide coupling and a subsequent highly E-selective RCM reaction. Macrolactam 3 could be converted into tetrabenazine in three known steps.

Oligo(N-alkoxy glycines): trans substantiating peptoid conformations

Peptoid oligomers possess many desirable attributes bioactive peptidomimetic agents, including their ease of synthesis, chemical diversity, and capability for molecular recognition. Ongoing efforts to develop functional peptoids will necessitate improved capability for control of peptoid structure, particularly of the backbone amide conformation. We introduce alkoxyamines as a new reagent for solid phase peptoid synthesis. Herein, we describe the synthesis of N-alkoxy peptoids, and present NMR data indicating that the oligomers adopt a single stable conformation featuring trans amide bonds. These findings, combined with results from computational modeling, suggest that N-alkoxy peptoid oligomers have a strong propensity to adopt a polyproline II type secondary structure.

The effect of backbone stereochemistry on the folding of acyclic beta(2, 3)-aminoxy peptides

As a new type of foldamer, beta-aminoxy peptides have the ability to adopt novel beta N--O turns or beta N--O helices in solution. Herein, we describe a new subclass of beta-aminoxy peptide, that is, peptides of acyclic beta(2, 3)-aminoxy acids (NH(2)OCHR(1)CHR(2)COOH), in which the presence of two chiral centers provides insight into the effect of backbone stereochemistry on the folding of beta-aminoxy peptides. Acyclic beta(2, 3)-aminoxy peptides with syn and anti configurations have been synthesized and their conformations investigated by NMR, IR, and circular dichroism (CD) spectroscopic, and X-ray crystallographic analysis. The beta N--O turns or beta N--O helices, which feature nine-membered rings with intramolecular hydrogen bonds and have been identified previously in peptides of beta(3)- and beta(2, 2)-aminoxy acids, are also predominantly present in the acyclic beta(2, 3)-aminoxy peptides with a syn configuration and N--O bonds gauche to the C(alpha)--C(beta) bonds in both solution and the solid state. In the acyclic beta(2, 3)-aminoxy peptides with an anti configuration, an extended strand (i.e., non-hydrogen-bonded state) is found in the solid state, and several conformations including non-hydrogen-bonded and intramolecular hydrogen-bonded states are present simultaneously in nonpolar solvents. These results suggest that the backbone stereochemistry does affect the folding of the acyclic beta(2, 3)-aminoxy peptides. Theoretical calculations on the conformations of model acyclic beta(2, 3)-aminoxy peptides with different backbone stereochemistry were also conducted to elucidate structural characteristics. Our present work may provide useful guidelines for the design and construction of new foldamers with predicable structures.

Peptides of aminoxy acids as foldamers

This Feature Article summarizes our efforts in developing a new family of foldamers from alpha-, beta- and gamma-aminoxy acids. From a series of conformational studies, we demonstrate that peptides consisting of aminoxy acids adopt several well-defined secondary structures, such as alpha N-O turns (which feature an eight-membered-ring hydrogen bond), beta N-O turns (a nine-membered-ring hydrogen bond), gamma N-O turns (a ten-membered-ring hydrogen bond), 1.8(8) helices (consecutive homochiral alpha N-O turns), 7/8 helices (alternating alpha N-O turns and gamma-turns), 1.7(9) helices (consecutive beta N-O turns), reverse turns (consecutive heterochiral alpha N-O turns) and sheet-like structures.