A novel neoglycopeptide building block

Bypassing Sulfonyl Halides: Synthesis of Sulfonamides from Other Sulfur-Containing Building Blocks

This review disclosed synthetic approaches to sulfonyl amides from non-sulfonyl halogenated precursors. Known methods were systematized into groups and subgroups according to the type of starting organosulfur compound. Thiols, disulfides, and sulfonamides form a group of S(II)-containing precursors, which are used in oxidative amination reactions. An important and versatile group for oxidative amination is represented with S(IV)-containing compounds, i. e., sufinates, sulfinamides, DMSO, N-sulfinyl-O-(tert-butyl)hydroxylamine, etc. A series of S(VI)-containing precursors for amination reactions (except sulfonyl halides) include sulfonic acids, sulfonyl azides, thiosulfonates, and sulfones. All approaches are represented with the most prominent examples of the resulting sulfonamides, which could be obtained in high yields mostly via short reaction sequences. Promising electrochemical methods for the preparation of sulfonamides from thiols, disulfides, sulfonamides, sulfinic acid derivatives, and dimethyl sulfoxide under mild and green conditions are also highlighted.

Hantzsch-Type Three-Component Approach to a New Family of Carbon-Linked Glycosyl Amino Acids. Synthesis of C-Glycosylmethyl Pyridylalanines,

C-Glycosylmethyl pyridylalanines reported in this paper constitute a novel family of glycosyl amino acids that contain a pyridine ring linking the carbohydrate and amino acid residues. These amino acids may serve to prepare nonnatural glycopeptides displaying firmly bound carbohydrate fragments through a rigid and highly stable tether. A viable route to these new hybrid molecules has been opened via thermally induced Hantzsch-type cyclocondensation using an aldehyde-ketoester-enamino ester system. To one of these reagents was attached a C-glycosyl residue, while to another was bound an amino acid fragment. In a one-pot optimized methodology, the dihydropyridine was not isolated while its purification was carried out by removal of unreacted material and side products using polymer-supported scavengers. Then the dihydropyridine (mixture of diastereoisomers) was oxidized by a polymer-bound oxidant to give the target pyridine bearing the two bioactive residues. In this way a range of eight compounds (58-68% yield) was prepared in which the elements of diversity were (i) the gluco and galacto configurations of the pyranose ring, (ii) the alpha- and beta-configurations at the anomeric center, and (iii) the positions of the carbohydrate and amino acid sectors in the pyridine ring. The orthogonal functional group protection in these amino acids allowed their easy incorporation into oligopeptides via sequential amino and carboxylic group coupling.

A New Scaffold for the Stereoselective Synthesis of α-O-Linked Glycopeptide Mimetics

alpha-O-Linked glycohomoglutamates are obtained as diastereomerically pure compounds by chemo-, regio-, and stereoselective cycloadditions between glycals and aspartic acid derivatives. The latter constitute orthogonally functionalized scaffolds for glycopeptide mimetics.

A Weinreb Nitrile Oxide and Nitrone for Cycloaddition

[reaction: see text] The cycloaddition of Weinreb amide functionalized nitrile oxide/nitrones with a range of dipolarophiles has been explored.

An o-Iminothioquinone: Its Cycloaddition To Produce an Indologlycoside and Its Self-Dimerization To Form a Dithio-Diazocycloctane, the Structure Assignment of Which Is Based on the DFT Prediction of Its IR Spectrum

An unusual heterodiene, an indolothiono quinone, undergoes cycloaddition with a glycal to form an indole-N-glycoside. A novel dimer of the indolothionoquinone is assigned its structure on the basis of a match between its predicted and observed IR spectrum.