An efficient synthesis of d-ribo- and l-lyxo-phytosphingosine from d-tartaric acid

The preparations of d-ribo- and l-lyxo-phytosphingosines (1, 2) are described. Chelation-controlled addition of tetradecylmagnesium bromide to pentylidene-protected d-threitol aldehyde 6 afforded the key intermediate tetrol 7, providing the desired l-lyxo stereochemistry of phytosphingosine. Inversion at C4 of intermediate 7 provided the d-ribo stereochemistry.     

From d-xylose to a d-glycero-l-altrose derivative

A key intermediate corresponding to a rare sugar framework has been synthesized, starting from d-xylose, an inexpensive carbohydrate. This approach gave access to new elaborated sugar moieties for structure–activity relationships in the KRN research.     

Asymmetric syntheses of the methyl glycosides of 2-deoxy-2-aminohexoses: d-allosamine, d-mannosamine, d-idosamine and d-talosamine

A range of the methyl glycosides of 2-deoxy-2-aminohexoses, comprising d-allosamine, d-mannosamine, d-idosamine and d-talosamine, were prepared from the corresponding d-aldopentoses via a seven step synthetic sequence. The doubly diastereoselective conjugate addition of the requisite antipode of lithium N-benzyl-N-(α-methylbenzyl)amide and in situ enolate oxidation with the requisite antipode of camphorsulfonyloxaziridine (CSO) was used as the key, stereodefining step. Sequential reduction of the resultant α-hydroxy-β-amino esters and oxidative cleavage of the C(1)–C(2) diol unit furnished the corresponding α-amino aldehydes. Subsequent N- and O-deprotection gave the target compounds (as mixtures of anomers) in good yield and high diastereoisomeric purity.     

A convenient synthesis of l-ribose from d-fructose

An efficient method for the stereoselective synthesis of l-ribose was accomplished starting from commercially inexpensive d-fructose. The intermediates in the process can serve as versatile precursors for the preparation of l-nucleoside analogues.     

Highly efficient stereoselective synthesis of d-erythro-sphingosine and d-lyxo-phytosphingosine

Starting from a single suitable functionalised epoxide, a highly efficient stereoselective synthesis of d-erythro-sphingosine and d-lyxo-phytosphingosine is described. The approach allows the formal preparation of all stereoisomers of these sphingoid structures.     

An efficient synthesis of selectively functionalized d-rhamnose derivatives

d-Rhamnose is an important component of bacterial lipopolysaccharides. This paper describes a short and highly efficient synthesis of d-rhamnose from d-mannose. The synthesis of selectively C-4 modified d-rhamnosides and 6-deoxy-d-talosides as potential building blocks for complex oligosaccharide synthesis is also discussed.     

Stereoselective synthesis of 3-glycosyl-5-methoxycarbonyl-isoxazolidines from d-galactose and d-glucose

Regio- and stereoselective cycloaddition of methyl acrylate to C-glycosyl nitrones derived from d-galactose and d-glucose, giving 5-methoxycarbonyl-3-(pentoglycos-5-yl or pentitol-1-yl)isoxazolidines, is reported. Transformation of one of them into a 4-hydroxy-2-(pentoglycos-5-yl)pyrrolidine derivative, potentially useful in a route to polyhydroxy-perhydroazaazulenes, was achieved.     

A proline-catalyzed aldol approach to the synthesis of 1-N-iminosugars of the d-glucuronic acid type

A new synthetic route to 1-N-iminosugars of glucuronic acid type (e.g., 1) has been developed employing proline-catalyzed aldol reaction as a key step.     

Novel practical synthesis of d-cycloserine

The synthesis of d-cycloserine has been successfully accomplished from the readily available d-serine through three simple and efficient routes. In each synthetic strategy, cyclization reactions are involved as the key step, and one-pot processes are employed. The simple treatment and mild reaction conditions are attractive features in this methodology.     

A highly efficient synthesis of unnatural l-sugars from d-ribose

A preparative and short synthesis of l-ribose and l-apiose was accomplished starting from d-ribose via stereoselective cis-dihydroxylation and C2-hydroxymethylation, respectively. These l-sugars can serve as versatile intermediates for the synthesis of l-nucleosides.     

A convenient approach to total synthesis of synargentolide-B from l-ascorbic acid and d-ribose

A convenient and practical approach for the total synthesis of naturally occurring lactone synargentolide-B has been accomplished in 14 steps from the commercially available l-ascorbic acid and d-ribose involving Bestmann–Ohira reaction, zinc mediated allylation, ring closing-metathesis, and cross-metathesis reactions. The highlight of our strategy describes a one-pot reaction involving stereoselective addition of allylzinc reagent and selective reduction of terminal alkyne to obtain the key advanced intermediates.     

New building blocks for peptide and depsipeptide synthesis: hexafluoroacetone protected l-homoisoserine and d,l-homoisocysteine derivatives

Efficient syntheses of l-homoisoserine and d,l-homoisocysteine derivatives starting from l-malic and d,l-thiomalic acid using hexafluoroacetone as protecting and activating agent are described. The new compounds are interesting building blocks for the preparation of non-natural peptides and depsipeptides as well as for the construction of new GABA derivatives.     

Tetrahydrofuran-mediated radical processes: stereoselective synthesis of d,l-hexestrol

The highly stereoselective synthesis of d,l-hexestrol (1), an inhibitor of microtubule assembly, is developed by using, as a key step, an intermolecular coupling of Co₂(CO)₆-complexed propargyl radicals. The latter are generated by novel complementary processes involving an interaction of tetrahydrofuran with Co₂(CO)₆-complexed propargyl alcohols and cations. An isomerically pure d,l-μ-η²-[3,4-di(4-methoxyphenyl)-1,5-hexadiyne]-bis-dicobalthexacarbonyl (d,l-6) is isolated in 69-91% yield with intermolecular coupling reactions exhibiting an excellent chemo- (0.5-7%) and d,l-diastereoselectivity (90-94%). The structure of d,l-6 is determined by X-ray diffraction. The subsequent steps include BBr₃-induced demethylation of 4-methoxyaryl groups, demetalation with cerium(IV) ammonium nitrate, and hydrogenation of acetylenic termini affording d,l-hexestrol (1).     

Binding of d-mannose to hydrogel matrix using isothiocyanate derivatives

Crosslinked hydrogels from 2-hydroxyethyl methacrylate (HEMA), ethylene dimethacrylate and polymerizable active esters based on N-methacryloylated ω-amino acids were prepared and modified with excess of ethane-1,2-diamine or hexane-1,6-diamine. 4-Isothiocyanatophenyl mannopyranoside or 6-(4-isothiocyanatobenzamido)hexyl mannopyranoside were used to bond d-mannose to hydrogel matrix through thioureylene groups.     

Total synthesis of d-(+)-biotin

A total synthesis of d-(+)-biotin is described starting from d-(+)-glucosamine using acyliminium chemistry.     

Improved synthesis of 6-amino-6-deoxy-d-galactono-1,6-lactam and d-mannono-1,6-lactam from corresponding unprotected d-hexono-1,4-lactones

Regioselective bromination of unprotected d-galactono-1,4-lactone and d-mannono-1,4-lactone with PPh₃/CBr₄ led to 6-bromo-6-deoxy derivatives. These intermediates were treated with LiN₃ and hydrogenated to give 6-amino-6-deoxy-d-galactono-1,6-lactam (8) and 6-amino-6-deoxy-d-mannono-1,6-lactam (13) in 74 and 67% overall yield, respectively.     

Enantioselective synthesis of d- and l-α-methylcysteine with hydantoinase

A scalable and cost-effective synthesis of d- and l-α-methylcysteine is described. A key step is d-selective cyclization of N-carbamoyl S-tert-butyl-d,l-α-methylcysteine catalyzed by hydantoinase. d-5-tert-Butylthiomethyl-5-methylhydantoin and N-carbamoyl S-tert-butyl-l-α-methylcysteine were obtained with excellent yield and optical purity, and these compounds were easily separated by filtration. After hydrolysis and cleavage of the tert-butyl group, d- and l-α-methylcysteine hydrochloride were obtained.     

A convenient synthesis of methyl N-acetyl-α-d-lividosaminide from d-glucal

Methyl N-acetyl-α-d-lividosaminide has been synthesised starting from 4,6-di-O-benzyl-d-glucal via a new nitro glucal derivative in six steps.     

Diastereoselective synthesis of d-xylo-isoxazolidinyl nucleosides

The condensation of the acetoxyisoxazolidines with silylated uracil, thymine, cytosine, N-acetylcytosine, and guanine proceeded in good yields and with moderate to good stereoselectivity to give isoxazolidinyl β- and α-nucleosides. The stereoselectivity of the addition is dependent on the structure of the substituent at C-3 originating from the starting chiral nitrone. The Vorbrüggen nucleosidation of isoxazolidine 8 at 70 °C afforded β-anomers as the exclusive nucleosides together with the isoxazoline 11. It was found that the nucleosidation proceeded also in methylene chloride at room temperature.     

A new simple route to deoxyamino sugars from non-sugar material: synthesis of d-tolyposamine and 4-epi-d-tolyposamine and formal synthesis of d-vicenisamine

A new, simple strategy has been formulated for the synthesis of deoxyamino sugars from a non-sugar starting material. Starting from the enantiomerically pure diol obtained from ethyl sorbate by Sharpless asymmetric dihydroxylation, the synthesis of two types of 2,3,4,6-tetradeoxy-4-amino sugars—d-tolyposamine and 4-epi-d-tolyposamine—, and formal synthesis of 2,4,6-trideoxy-4-amino sugar—d-vicenisamine—were performed.