[Au]/[Ag]-Catalyzed Glycosidation of Ethynylcyclohexyl Glycosyl Carbonates Enables Direct Stereoselective Synthesis of 2-Azido-2-deoxy-β-mannopyranosides.

We describe the [Au]/[Ag]-catalyzed activation of ethynylcyclohexyl 2-azido-4,6--benzylidene mannosyl carbonates for β-mannosamine linkage preparation in high yield and selectivity in a temperature- and concentration-dependent manner. VT-NMR studies reveal an anomeric triflate intermediate generated in the absence of an acceptor alcohol that is stable up to -10 °C. The generality of the protocol was illustrated by successful application to a series of acceptors and by synthesis of a fully protected type 19F capsular trisaccharide.

Silver-assisted gold-catalyzed solid phase synthesis of linear and branched oligosaccharides.

Unlike solid phase synthesis of peptides, synthesis of oligosaccharides by solid phase methods is lagging behind owing to inherent challenges faced while executing glycosidations. In this communication, silver-assisted gold-catalyzed glycosidations are found to be excellent for solid phase oligosaccharide synthesis. Glycosidations under catalytic conditions, one time coupling with four equivalents of donor, reactions in less than 30 min at 25 °C and on-resin deprotection of silyl and benzoate protecting groups are the salient features.

AuBr-catalyzed azidation of per--acetylated and per--benzoylated sugars.

Herein we report, for the first time, the successful anomeric azidation of per--acetylated and per--benzoylated sugars by catalytic amounts of oxophilic AuBr in good to excellent yields. The method is applicable to a wide range of easily accessible per--acetylated and per--benzoylated sugars. While reaction with per--acetylated and per--benzoylated monosaccharides was complete within 1-3 h at room temperature, the per--benzoylated disaccharides needed 2-3 h of heating at 55 °C.

-Nitrophenyl carbonate promoted ring-opening reactions of DBU and DBN affording lactam carbamates.

The amidine bases DBU (1,8-diazabicyclo[5.4.0]undec-7-ene) and DBN (1,5-diazabicyclo[4.

Synthesis of D-fructose-derived spirocyclic 2-substituted-2-oxazoline ribosides.

The TMSOTf-mediated synthesis of β-configured spirocyclic 2-substituted-2-oxazoline ribosides was achieved using a "Ritter-like" reaction in toluene through nucleophilic addition of electron-rich nitriles to the oxacarbenium ion intermediate of 1,2;3,4-di-O-isopropylidene-β-D-psicofuranose derivatives with concomitant intramolecular trapping of the C2 hydroxymethyl group on the electrophilic nitrilium carbon. These carbohydrate-derived spirooxazolines are stable and were obtained in good yield with high stereoselectivity due to the conformational rigidity imparted by the 3,4-isopropylidene group.

Halogenated D-xylono-δ-lactams: synthesis and enzyme inhibition study.

A concise synthesis of four C-3 fluoro/chloro-D-xylono-δ-lactams 3/4 has been reported. The methodology involves Corey-Link approach with suitably protected 3-oxo-D-gluco-furanose to introduce F/Cl as well as ester/amide functionalities at C-3 of glucose. In next steps, 5,6-O-isopropylidene group was converted to the 5-azido xylosugars that on opening of 1,2-acetonide group, and intramolecular Schmidt-Boyer reaction with TFA/H2O, in one pot, afforded lactams 3/4.

Sugar furanoid trans-vicinal diacid as a γ-turn inducer: synthesis and conformational study.

A simple method for the synthesis of a sugar furanoid trans vicinal diacid and its incorporation into the N-terminal tetrapeptide sequence (H-Phe-Trp-Lys-Thr-OH) to get glycopeptide has been described. 2D NMR and MD simulation studies of clearly show that the sugar diacid adopts a γ-turn conformation towards the N-terminus.

Design and synthesis of dephosphono DNA analogues containing 1,2,3-triazole linker and their UV-melting studies with DNA/RNA.

This article describes the synthesis of 3'/5' linked 1,2,3-triazolyl dithymidine derivatives, their incorporation into oligonucleotides, and evaluation of their thermal stabilities toward complementary DNA/RNA.

Design, synthesis and DNA/RNA binding studies of nucleic acids comprising stereoregular and acyclic polycarbamate backbone: polycarbamate nucleic acids (PCNA).

The designed, chiral, acyclic polycarbamate nucleic acids (PCNA) exhibited sequence and orientation specific binding to nucleic acids. Complexes of PCNA with DNA were as stable as PNA:DNA complexes and those with RNA were as stable as natural DNA:RNA complexes.

Exploring the hand test with medically ill children and adolescents.

Pediatric psychologists use the tools of assessment to evaluate the psychological functioning of youth with chronic and acute medical illnesses. This study is an exploration of the use of a performance-based measure, the Hand Test (HT; Wagner, 1983), with pediatric medical patients. A sample of medical inpatients (n = 27) and psychiatric outpatients (n = 24) were administered the HT, a self-report measure, and a parent-report behavior rating scale.