Cyclic Thiocarbamates Research Articles

Seed coat composition in black and white soybean seeds with differential water permeability.

The seed coat composition of white (JS 335) and black (Bhatt) soybean (Glycine max (L.) Merr) having different water permeability was studied. Phenols, tannins and proteins were measured, as well as trace elements and metabolites in the seed coats. The seed coat of Bhatt was impermeable and imposed dormancy, while that of JS 335 was permeable and seeds exhibited imbibitional injury. Bhatt seed coats contained comparatively higher concentrations of phenols, tannins, proteins, Fe and Cu than those of JS 335. Metabolites of seed coats of both genotypes contained 164 compounds, among which only 14 were common to both cultivars, while the remaining 79 and 71 compounds were unique to JS 331 and Bhatt, respectively. Phenols are the main compounds responsible for seed coat impermeability and accumulate in palisade cells of Bhatt, providing impermeability and strength to the seed coat. JS 335 had more cracked seed coats, mainly due to their lower tannin content. Alkanes, esters, carboxylic acids and alcohols were common to both genotypes, while cyclic thiocarbamate (1.07%), monoterpene alcohols (1.07%), nitric esters (1.07%), phenoxazine (1.07%) and sulphoxide (1.07%) compounds were unique to the JS 335 seed coat, while aldehydes (2.35%), amides (1.17%), azoles (1.17%) and sugar moieties (1.17%) were unique to Bhatt seed coats. This study provides a platform for isolation and understanding of each identified compound for its function in seed coat permeability.

Chiral N,N′‐Dioxide–Yttrium Triflate Complexes‐Catalyzed Asymmetric Aldol Cyclization of α‐Keto Esters with α‐Isothiocyanato Imide

AbstractA highly effective aldol cyclization of α‐isothiocyanato imide to both β,γ‐unsaturated α‐keto esters and aryl‐substituted α‐keto esters has been developed. A chiral N,N′‐dioxide–yttrium triflate complex was used as the catalyst. A series of cyclic thiocarbamates bearing chiral quaternary stereocenters was synthesized in good to high yields, excellent diastereo‐ (up to 25:1 dr) and enantioselectivities (up to 99 % ee). In addition, the reaction could be carried out on a gram‐scale, and other functionalized derivatives are also conveniently transformed. Interestingly, a discrepancy of diastereoselection was observed between the reactions of β,γ‐unsaturated α‐keto esters and aryl‐substituted α‐keto esters. Moreover, a substrate dependency of non‐linear effects was observed in this reaction. On the basis of the experimental results and the absolute configuration of the products, possible catalytic models have been proposed to explain the origin of the asymmetric process.magnified image

ChemInform Abstract: Direct Organocatalytic Asymmetric Aldol Reaction of α‐Isothiocyanato Imides to α‐Ketoesters under Low Ligand Loading: A Doubly Stereocontrolled Approach to Cyclic Thiocarbamates Bearing Chiral Quaternary Stereocenters.

AbstractThe title reaction provides a new and convenient method to prepare synthetically important cyclic thiocarbamates with good to high diastereo‐ and enantioselectivity.

ChemInform Abstract: Synthesis of 6,7-Dideoxy-7-isothiocyanatoheptoses: Stable Fully Unprotected Monosaccharide Isothiocyanates.

Abstract Methyl 6,7-dideoxy-7-isothiocyanato-α- d - gluco ( manno )( galacto )-heptopyranosides have been synthesized in four steps by homologation of the respective methyl hexopyranosides via the corresponding heptopyranosydurononitriles. Neither intra- nor intermolecular thiocarbamate formation was observed, even under rather strenuous acidic or basic conditions. The reducing derivative 6,7-dideoxy-7-isothiocyanato-α- d - gluco -heptopyranose was also a stable compound in aqueous solution in the absence of base. Formation of a six-membered intramolecular cyclic thiocarbamate was achieved in DMF solution in the presence of triethylamine. The title compounds are the first examples of stable fully unprotected monosaccharide isothiocyanates.

Direct Organocatalytic Asymmetric Aldol Reaction of α-Isothiocyanato Imides to α-Ketoesters under Low Ligand Loading: A Doubly Stereocontrolled Approach to Cyclic Thiocarbamates Bearing Chiral Quaternary Stereocenters

The first doubly stereocontrolled organocatalytic asymmetric aldol reaction of alpha-isothiocyanato imides with alpha-ketoesters by using rosin-derived tertiary amine-thiourea under low ligand loading to form cyclic thiocarbamates bearing quaternary stereogenic centers with high levels of enantio- and diastereoselectivity (up to 99% ee, and 97:3 dr) is presented. This reaction provides a convenient doubly stereocontrolled method to access synthetic useful multiply substituted cyclic thiocarbamates with high optical purity.

Synthesis of 6,7-dideoxy-7-isothiocyanatoheptoses: stable fully unprotected monosaccharide isothiocyanates

Methyl 6,7-dideoxy-7-isothiocyanato-α- d- gluco( manno)( galacto)-heptopyranosides have been synthesized in four steps by homologation of the respective methyl hexopyranosides via the corresponding heptopyranosydurononitriles. Neither intra- nor intermolecular thiocarbamate formation was observed, even under rather strenuous acidic or basic conditions. The reducing derivative 6,7-dideoxy-7-isothiocyanato-α- d- gluco-heptopyranose was also a stable compound in aqueous solution in the absence of base. Formation of a six-membered intramolecular cyclic thiocarbamate was achieved in DMF solution in the presence of triethylamine. The title compounds are the first examples of stable fully unprotected monosaccharide isothiocyanates.

N-Thiocarbonyl azasugars: a new family of carbohydrate mimics with controlled anomeric configuration

Bicyclic azasugar glycomimetics structurally related to the polyhydroxy-indolizine and -piperidine series incorporating a stereoelectronically controlled pseudoanomeric axial hydroxy group have been prepared by tautomeric rearrangement of cyclic thiocarbamate precursors; preliminary enzyme inhibition tests show an increased selectivity towards yeast α-glucosidase for the α-D-glucopyranose analogue as compared with castanospermine or nojirimicin.

Isothiocyanates and cyclic thiocarbamates of α, α′-trehalose, sucrose, and cyclomaltooligosaccharides

6,6′-Dideoxy-6,6′-diisothiocyanato-α, α′-trehalose ( 4), 6-deoxy-6-isothiocyanato-α- d-fructofuranose β- d-fructopyranose 1,2′:2,1′-dianhydride ( 11), 6,6′-dideoxy-6,6′-diisothiocyanatosucrose ( 16), and per(6-deoxy-6-isothiocyanato)-cyclomaltohexaose ( 23), -cyclomaltoheptaose ( 27), and -cyclomaltooctaose ( 31) have been prepared in high yield by reaction of the corresponding amino sugars with thiophosgene. In the absence of base, all isothiocyanates were stable and could be stored and acetylated without decomposition. In the presence of triethylamine, 6,6′-dideoxy-6,6′-diisothiocyanato-α, α′-trehalose underwent intramolecular cyclisation involving HO-4 to give the corresponding bis(cyclic thiocarbamate). The product of cyclisation at a single glucopyranosyl unit was obtained in the treatment of the above diisothiocyanate with mixed (H +, HO −) ion-exchange resin. Under identical reaction conditions, 6,6′-dideoxy-6,6′-diisothiocyanatosucrose yielded exclusively the product of intramolecular cyclisation at the d-glucopyranosyl moiety, while derivatives of α- d-fructofuranose β- d-fructopyranose 1,2′:2,1′-dianhydride and cyclomaltooligosaccharides remained unchanged.