4,6-O-benzylidene-D-glucopyranose and its sodium salt: new data on their preparation and properties

Marine Toxins with Spiroimine Rings: Total Synthesis of Pinnatoxin A

This microreview provides a compilation of synthetic approaches and total syntheses of pinnatoxin A in a survey of the literature up to early 2010. Pinnatoxin A is the first discovered and representative member of a fascinating group of potent marine toxins that share a spiroimine subunit as a unifying structural element.

Zwitterionic glycosidase inhibitors: salacinol and related analogues

Natural products with interesting biological properties and structural diversity have often served as valuable lead drug candidates for the treatment of human diseases. Salacinol, a naturally occurring alpha-glucosidase inhibitor, was shown to be one of the active principles of the aqueous extract of a medicinal plant that has been prescribed traditionally as an Ayurvedic treatment for type II diabetes. Salacinol contains an intriguing zwitterionic sulfonium-sulfate structure that comprises a 1,4-anhydro-4-thio-D-arabinitol core and a polyhydroxylated acyclic chain. Due to the unique structural features and its potential to become a lead drug candidate in the treatment of type II diabetes, a great deal of attention has been focused on salacinol and its analogues. Since the isolation of salacinol, several papers describing various synthetic routes to salacinol and its analogues have appeared in the literature. This review is aimed at highlighting the synthetic aspects of salacinol and related compounds as well as their structure-activity relationship studies.

Synthesis of benzylidenated hexopyranosides in ionic liquids

The synthesis of 4,6-O-benzylidenated monosaccharides and disaccharides has been studied using ionic liquids as a unique solvent alternative. An examination of several imidazolium ionic liquids indicates that the benzylidenation of hexopyranosides in 3-butyl-1-methylimidazolium tetrafluoroborate, [bmim]BF4, gives the highest yields for most of the substrates, and that this solvent system could be readily recycled.

Regioselective synthesis of vinylic derivatives of common monosccarides through their activated stannylene acetal intermediates

The regioselective C-2-O-acrylation and metacrylation of methyl 4,6-O-benzylidene-α-D-glucopyranoside and methyl 4,6-O-benzylidene-α-D-galactopyranoside through their corresponding organotin intermediates have been studied. Regioselectivity was achived through the formation of a tin chelate of the 2,3-diols. Thus, methyl 4,6-O-benzylidene-α-D-glucopyranoside and methyl 4,6-O-benzylidene-α-D-galactopyranoside were reacted with dibutylstannylene to give the corresponding dibutylstannylene acetal intermediates that were then reacted in a regioselective manner with acryloyl chloride or metacryloyl chloride in the presence of triethylamine (TEA) or pyridine to give the vinylic type monomeric compounds. The monomeric products containing glucose and galactose units from each reaction were separated by column chromatography using a gradient of n-hexane and ethyl acetate as eluant. The structure of the obtained compounds were confirmed using ¹H-, ¹³C- and 2D NMR spectroscopy.

Synthesis of a nitrogen analogue of salacinol and its alpha-glucosidase inhibitory activity

A nitrogen analogue 4 of the naturally occurring sulfonium ion salacinol (1), a potent alpha-glucosidase inhibitor isolated from the Ayruvedic medicine Salacia reticulata, was synthesized and its inhibitory activity against alpha-glucosidase tested. Substitution of the sulfur atom in 1 with a nitrogen reduced the activity considerably. The solid-state stereostructure of the related compound (5) was determined on the basis of single crystal X-ray measurement.

Synthesis and characterisation of N-glycosyl amines from the reaction between 4,6-O-benzylidene-D-glucopyranose and substituted aromatic amines and also between 2-(o-aminophenyl)benzimidazole and pentoses or hexoses

Twelve N-glycosyl amines were synthesised using 4,6-O-benzylidene-D-glucopyranose and different substituted aromatic amines, including some diamines that resulted in bis-glycosyl amines. Another set of six N-glycosyl amines was synthesised using different hexoses and pentoses and 2-(o-aminophenyl)benzimidazole. All compounds were isolated as solid products and purified, their elemental compositions were established, and these were characterised by NMR (1H and 13C), UV-Vis, and FTIR spectroscopy, by FAB mass spectrometry (molecular-ion peaks gave molecular weights), and by their optical rotations. While the protected saccharide, 4,6-O-benzylidene-D-glucopyranose, exists as a mixture of beta and alpha anomers in solution, the corresponding N-glycosyl amines were of only the beta anomeric form as determined by NMR and FTIR spectroscopy. On the other hand, N-glycosyl amines synthesised from 2-(o-aminophenyl)benzimidazole prefer the alpha anomeric form, and in two cases a mixture of both the beta and the alpha anomers were observed. The trends observed in the chemical shifts were compared among different products.

Synthesis and anticancer activity of novel chiral D-glucose derived bis-imidazoles and their analogs

A series of novel D-glucose derived bis-imidazoles and their analogs, which possess potential in bioorganic and supramolecular chemistry, were designed and synthesized from methyl alpha-D-glucoside through protection, bis-bromination, N-alkylation and deprotection. All new compounds were characterized by HRMS, 1H, 13C and DEPT NMR spectroscopy as well as elemental analysis. The 1H-(1)H and 1H-(13)C 2D NMR spectra for some compounds were also recorded. Some regular features of 13C and 1H NMR spectra were summarized. The anticancer activity of some compounds was evaluated.

Ring-closing alkyne metathesis. Application to the total synthesis of sophorolipid lactone

The first total synthesis of a major component of the microbial biosurfactant sophorolipid has been achieved. This approach to the 26-membered macrolide 1 containing a Z-configured alkene group in its lipidic tether spanning the sophorose backbone is based on a ring-closing metathesis reaction of diyne 21 catalyzed by Mo[N(t-Bu)(Ar)](3) (5; Ar = 3,5-dimethylphenyl) activated in situ by CH(2)Cl(2), followed by Lindlar reduction of the resulting cycloalkyne 22. The two beta-glycosidic linkages of compound 21 were installed by means of the glucal epoxide method and a modified Koenigs-Knorr reaction promoted by AgOTf/lutidine, respectively.