Regioselective Oxidative Cleavage of Benzylidene Acetals: Synthesis of α- and β-Benzoyloxy Carboxylic Acids

Synthesis and Bioassay of Neurogenically Potent Gangliosides DSG-A, Hp-s1 and Their Analogues

In the search of a potent candidate for neurotherapy, we designed and synthesized various analogues of ganglioside Hp-s1. The modification includes the change in hydrophobicity by varying the carbon chain length, altering the number of hydrogen bonds, and replacing the anomeric atom. The chemical synthesis was carried out by using various methods and discussed in details. The neuritogenic activities of these analogues are confirmed in a human neuroblastoma cell line SH-SY5Y. A higher activity of ganglioside Hp-s1 analogue on IL-17A transcript upregulation than ganglioside Hp-s1 was found.

Iminosugar C-Nitromethyl Glycoside: Stereoselective Synthesis of Isoxazoline and Isoxazole-Fused Bicyclic Iminosugars

A simple and efficient method for the stereoselective synthesis of isoxazoline/isoxazole-fused iminosugar derivatives has been developed using intramolecular nitrile oxide cycloaddition (INOC) as a key step. Iminosugar C-nitromethyl glycosides, derived from simple carbohydrates, served as excellent nitrile oxide precursors in 1,3-dipolar cycloaddition reactions. N-Alkenyl iminosugar C-nitromethyl glycosides afforded novel isoxazoline-fused indolizidine-, pyrrolizidine-, and quinolizidine-based iminosugars in excellent yields with a high degree of stereoselectivity, whereas N-alkynyl iminosugar C-nitromethyl glycosides furnished the corresponding isoxazole containing tricyclic iminosugars in very good yields.

Metal-free one-pot α-carboxylation of primary alcohols

An efficient metal-free procedure for the formal α-carboxylation of primary alcohols has been developed. The method involves a one-pot oxidation/Passerini/hydrolysis sequence and provides access to α-hydroxy acids bearing a broad range of functional groups. A minor modification to the reaction conditions extends the range of accessible products to α-hydroxy esters.

Benzylidene Acetal Protecting Group as Carboxylic Acid Surrogate: Synthesis of Functionalized Uronic Acids and Sugar Amino Acids

Direct oxidation of the 4,6-O-benzylidene acetal protecting group to C-6 carboxylic acid has been developed that provides an easy access to a wide range of biologically important and synthetically challenging uronic acid and sugar amino acid derivatives in good yields. The RuCl3 -NaIO4 -mediated oxidative cleavage method eliminates protection and deprotection steps and the reaction takes place under mild conditions. The dual role of the benzylidene acetal, as a protecting group and source of carboxylic acid, was exploited in the efficient synthesis of six-carbon sialic acid analogues and disaccharides bearing uronic acids, including glycosaminoglycan analogues.

A chemoselective oxidation of monosubstituted ethylene glycol: facile synthesis of optically active α-hydroxy acids

A mild and efficient method for the chemoselective oxidation of monosubstituted ethylene glycols to optically active α-hydroxy acids has been achieved using the TEMPO–NaOCl reagent system.

Resolution of carboxylic acids using copper(I)-promoted removal of propargylic esters under neutral conditions

A method for the optical resolution of carboxylic acids is described. Condensation of racemic carboxylic acids with chiral terminal propargyl alcohols gave separable diastereomeric esters. Chromatographic separation followed by heating the individual diastereomers in methanol with catalytic copper(I) halide regenerated the carboxylic acids in good yields and in enantiomeric ratios of ≥94%. This method is particularly useful for the resolution of carboxylic acids that are incompatible with conventional ester hydrolysis.

Synthesis of (-)-deoxoprosophylline, (+)-2-epi-deoxoprosopinine, and (2R,3R)- and (2R,3S)-3-hydroxypipecolic acids from D-glycals

New syntheses of (-)-deoxoprosophylline, (+)-2-epi-deoxoprosopinine, and (2R,3R)- and (2R,3S)-3-hydroxypipecolic acids are reported. Utilization of the chiral functionalities of Perlin aldehydes, derived from 3,4,6-tri-O-benzyl glycals, has been done along with chemoselective saturation of olefins and reductive aminations as key steps.