A General Methodology for Automated Solid-Phase Synthesis of Depsides and Depsipeptides. Preparation of a Valinomycin Analogue

Solid-phase synthesis of methyl carboxymycobactin T 7 and analogues as potential antimycobacterial agents

A solid-phase approach for the total synthesis of methyl carboxymycobactins 1a-d, with an on-resin cyclization leading to azopine 5 as the key step, was developed. The iron-affinity of these compounds was assessed by a competitive sulfoxine-binding assay, and antimycobacterial activity was tested against the growth of Mycobacterium avium.

The cyclization of peptides and depsipeptides

Constricting the peptide backbone into a more defined conformational form through cyclization is an activity evolved in nature and in synthetic work, the latter straddling only the most recent decades. The resulting conformational constraints increase the probability of an optimum response with bio-receptors. The purpose of this review is to highlight developments that have proved to be reasonably efficient in the macrocyclization of linear precursors into cyclic peptides and depsipeptides.

Solid phase library synthesis of cyclic depsipeptides: aurilide and aurilide analogues

A solid-phase combinatorial synthesis approach toward the cyclic depsipeptide aurilide (1) and related analogues is described. The peptide moiety 2 was assembled on trityl linker-functionalized SynPhase Crowns using an Fmoc strategy. Optimization of the tetrapeptide assembly 5 was carried out using parallel multiple synthesis and LC/MS analysis. The aliphatic moiety 3a was coupled with the solid-supported 2 using DIC/HOBt. Following deprotection and cleavage of linear precursor 26, macrocyclization was achieved under high dilution conditions. Removal of the methylthiomethyl protecting group provided aurilide (1) in 11% overall yield. Synthesis of a combinatorial library of aurilide derivatives 4 was accomplished with a similar protocol using the TranSort technique.

Synthesis, characterization and immunochemical evaluation of cephalosporin antigenic determinants

Lack of knowledge of the exact chemical structure of cephalosporin antigenic determinants has hindered clinical interpretation of adverse reactions to these drugs and delayed understanding of the mechanisms involved in the specific recognition and binding of IgE molecules to these antigenic determinants. We further resolve the relationship between structure and activity of proposed antigenic chemicals, including the rational design and synthesis of these haptenic structures. Comparative RAST inhibition studies of the synthesized molecules revealed that they were recognized by IgE antibodies induced by cephalosporin antibiotics. Thus, these data indicate that recognition is mainly directed to the acyl side chain and to the beta-lactam fragment that remains linked to the carrier protein in the cephalosporin conjugation course.

An improved method for the preparation of 3-O-benzyl-6-O-pivaloyl-alpha-D-glucopyranose 1,2,4-orthopivalate

The synthetic route to 3-O-benzyl-6-O-pivaloyl-alpha-D-glucopyranose 1,2,4-orthopivalate (1), which was previously established, was shortened by introducing two novel reactions, regioselective pivaloylation with dibutyltin oxide in toluene for the regioselective activation of hydroxyl groups, and intramolecular orthoesterification with benzenesulfonyl chloride and triethylamine in dichloromethane. Compound 1 was obtained in 58.8% overall yield from commercially available 1,2:5,6-di-O-isopropylidene-alpha-D-glucopyranose (2) via four reaction steps.