Efficient Synthesis of Rare Sugar d-Allal via Reversal of Diastereoselection in the Reduction of Protected 1,5-Anhydrohex-1-en-3-uloses: Protecting Group Dependence of the Stereoselection

NFSI mediated C3-ether oxidation of glycals for the synthesis of hex-3-enuloses

Hex-3-enuloses constitute a vital carbohydrate synthetic intermediate that provide access to wide range of chiral molecules through diverse derivatizations. Herein we report synthesis of these fascinating scaffolds by oxidation of C3-ether protections on glycals in presence of N-fluorobenzenesulfonimide (NFSI) under Cu(I) catalysed conditions. Benzyl, methyl and silyl ethers have been efficiently oxidized to the carbonyl group. The oxidation has been found to be highly regioselective where an array of protecting groups were tolerant to the reaction conditions. Pyranosyl glycals from various commercially available sugars have been studied in this work to evaluate the broad substrate scope.

Versatile applications of 3-OxoGlycals: A review

3-Oxoglycals are versatile building blocks with extensive applications in glycochemistry, organic, and bio-organic sciences. They serve as powerful synthons, enabling the development of diverse organic structures. This review highlights the utility of easily obtainable 3-oxoglycals as fundamental building blocks for synthesizing various compounds, including rare sugars, N-inserted compounds, fused heterocycles, medium ring compounds, polycyclic molecules, cycloadducts, and axially chiral molecules. Some of these compounds exhibit significant biological activities, while others possess valuable photophysical properties. The simplicity of these reactions, using readily available starting materials under favorable conditions, makes 3-oxoglycals a valuable tool for creating novel molecules, benefiting the scientific community in various fields.

Synthesis of Hexenuloses and a Library of Disaccharides Possessing 3-oxo-glycal Unit

An expeditious method for the synthesis of monosaccharides and disaccharides possessing 3-oxo-glycal units is revealed. Several monosaccharides and disaccharide-derived glycals are converted to the corresponding hexenuloses in three steps involving halo-alkoxylation, dehydrohalogenation, and ketalyzation reactions. A number of 3-oxo-glycals are synthesized to show the methodology's importance and generality. Further, the protocol is successfully applied to synthesize a rare-sugar disaccharide donor unit present as part of the trisaccharide moiety in the reported natural product, versipelostatin.

TEMPO-Catalyzed Oxidation of 3- O-Benzylated/Silylated Glycals to the Corresponding Enones Using a PIFA-Water Reagent System

A simple, highly efficient and regiospecific method for the direct conversion of 3- O-benzylated as well as silylated glycals into the corresponding enones has been developed using PIFA-TEMPO and water reagent system. The reaction is scalable on a gram scale under mild conditions with a yield up to 86%.

Selective Synthesis of Partially Protected d-Talopyranosides and d-Gulopyranosides via Catalytic Asymmetric Dihydroxylation: Multiplier Effects of Substrate Control and Catalyst Control

Highly selective syntheses of d-talopyranosides and d-gulopyranosides have been achieved by utilizing the multiplier effects of substrate control and catalyst control. Through the combination of an O-benzoyl-protected substrate and the AD-mix-β system, the d-talopyranoside was obtained in a ratio of 96:4. In contrast, the d-gulopyranoside was obtained in a ratio of 3:97 through the use of an O-tert-butyldimethylsilyl-protected substrate and AD-mix-α.

Scapiformolactones A-I: germacrane sesquiterpenoids with an unusual Δ3-15,6-lactone moiety from Salvia scapiformis

Nine germacrane sesquiterpenoids with an unusual Δ(3)-15,6-lactone moiety, scapiformolactones A-I (1-9), and one known seco-germacrane sesquiterpenoid, 3,7,11-trimethyldodeca-l,6,9-triene-3,11-diol (10), were isolated from whole plants of Salvia scapiformis Hance. Their structures were elucidated by spectroscopic methods including HR-ESIMS, IR, UV, NMR, and CD, as well as by quantum mechanical calculations and chemical transformations. Structures of compounds 1-3 were also confirmed by single-crystal X-ray diffraction analysis. Six germacrane 6,15-diol derivatives (11-16) were obtained by chemical transformation. Compounds 1-9 and 11-16 were evaluated for their in vitro immunomodulatory effects on T and B cells, as well as their in vitro cytotoxicity against five human cancer cell lines, HL-60, SMMC-7721, A-549, MCF-7, and SW480.

Cellulose recycling as a source of raw chirality

Modern organic chemistry requires easily obtainable chiral building blocks that show high chemical versatility for their application in the synthesis of enantiopure compounds. Biomass has been demonstrated to be a widely available raw material that represents the only abundant source of renewable organic carbon. Through the pyrolitic conversion of cellulose or cellulose-containing materials it is possible to produce levoglucosenone, a highly functionalized chiral structure. This compound has been innovatively used as a template for the synthesis of key intermediates of biologically active products and for the preparation of chiral auxiliaries, catalysts, and organocatalysts for their application in asymmetric synthesis.

Studies on the Zn(II)-mediated electrophilic selenocyclization and elimination of 3,4-O-isopropylidene-protected hydroxyalkenyl sulfides: synthesis of a 2-phenylselenenyl glycal

Herein, we describe a mild and efficient Zn(II)-mediated electrophilic selenocyclization reaction of readily available and stable 3,4-O-isopropylidene-protected hydroxyalkenyl sulfides to 2-deoxy-2-phenylselenenyl-1-thio-glycosides. This material was transformed into a 2-phenylselenenyl glycal in a controlled manner using an activation-elimination sequence.