Total synthesis of d-(+)-biotin

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

Stereoselective syntheses of (+)-proto, (−)-gala quercitols and carba-l-rhamnose from d-(−)-quinic acid

Efficient syntheses of (+)-proto, (−)-gala quercitols and carba-l-rhamnose from d-(−)-quinic acid are described.     

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.     

An efficient synthesis of 1,4-dideoxy-1,4-imino-d- and l-arabinitol and 1,4-dideoxy-1,4-imino-d- and l-xylitol from chiral aziridines

A highly efficient method for the synthesis of 1,4-dideoxy-1,4-imino-d- and l-arabinitol (d-AB1, 1 and l-AB1, 3) and 1,4-dideoxy-1,4-imino-d- and l-xylitol (d-DIX, 2 and l-DIX, 4) starting from commercially available chiral aziridines was developed. The general strategy employs a sequence involving two-carbon homologation, dihydroxylation, and regioselective aziridine ring opening/intramolecular five-membered iminosugar ring formation. The facile use of recrystallization to generate pure diastereomers makes the routes more amenable to large-scale synthesis.     

Highly stereoselective and stereospecific syntheses of a variety of quercitols from d-(−)-quinic acid

The highly stereoselective synthesis of (−)-epi-, (−)-allo- and neo-quercitols as well as stereospecific synthesis of (−)-talo- and (+)-gala-quercitols have been achieved. The general strategy is employing dihydroxylation of the isolated double bond of various kinds of protected chiral (1,4,5)-cyclohex-2-ene-triols, which are derived from d-(−)-quinic acid. The choosing of protecting groups from either BBA (butane 2,3-bisacetal) or acetyl groups will result in the various degrees of stereoselectivity of dihydroxylation. On the other hand, the cyclohexylidene acetal moiety is attributed to the stereospecificity during dihydroxylation to afford the request molecules.     

Novel synthesis of 5-thio-hexopyranoside: preparation of 5-thio-d- and l-glucose and 1,6-anhydro-5-thio-l- and d-altrose

Asymmetric synthesis of both d- and l-isomers of 5-thioglucose and 1,6-anhydro-5-thioaltrose are described. The key intermediates, l- and d-threose diethylacetal derivatives, were derived by chemical transformation from d-xylose or d-arabinose and by Sharpless asymmetric dihydroxylation from γ-hydroxycrotylaldehyde diethylacetal. They transformed to γ-thiiranyl diethylacetal via trans-2,3-epoxy alcohol in seven steps. Acetic acid-promoted cyclization of γ-thiiranyl diethylacetal gave 5-thiopyranoside. Removal of the protected groups under the acidic conditions afforded 5-thio-d- and l-glucose and 1,6-anhydro-5-thio-l- and d-altrose, respectively.     

Total synthesis of (+)-lentiginosine from d-glucose

A total synthesis of (+)-lentiginosine, a potent and selective amyloglucosidase inhibitor, is reported from a d-glucose-derived epoxide in 38% overall yield. In this synthesis, ambient conditions and readily available starting materials and reagents are used.     

Total synthesis of (+)-galanthamine starting from d-glucose

The stereoselective total synthesis of (+)-galanthamine (+)-1 starting from d-glucose is described. The cyclohexene ring in (+)-1 was prepared in an optically active form from d-glucose using Ferrier’s carbocyclization reaction, and the critical quaternary carbon was stereoselectively generated via chirality transfer based on the Claisen rearrangement of a cyclohexenol. The dibenzofuran skeleton was effectively constructed by the bromonium ion-mediated intramolecular cyclization of a cyclohexene possessing a phenolic ether function. After the introduction of a carbon-carbon double bond, the Pictet-Spengler type cyclization, followed by the reduction of the amide function completed the chiral synthesis of (+)-1.     

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.     

Practical synthesis of d-[1-C]mannose, l-[1-C] and l-[6-C]fucose

The chemical synthesis of ¹³C-labeled mannose and fucose is important for the preparation of molecular probes used in the conformational study of the oligosaccharide portions of glycoproteins. A new method for the synthesis of the title [1-¹³C]-labeled compounds via the corresponding olefin compounds, which are in turn derived from d-mannitol or l-arabinose by efficient introduction of ¹³C, by the Wittig reaction using Ph₃P¹³CH₃I and n-BuLi, is described. The introduction of ¹³CH₃I to produce the [1-¹³C]- and [6-¹³C]-labeled compounds was accomplished in 62%, 56%, and 71% yields, respectively. All mannose and fucose protons, from H-1 to H-6, were observed by the HMQC-TOCSY technique using 1:1 mixtures of [1-¹³C]- and [6-¹³C]-labeled compounds.     

Enantiodivergent synthesis of (−)-methylenolactocin and (+)-methylenolactocin from d-mannitol

An enantiodivergent synthesis of both enantiomers of methylenolactocin is described through stereocontrolled addition of n-pentyl magnesium bromide to two d-mannitol-derived diastereomerically related aldehydes having an α-chiral center with a β hetero atom.     

Total synthesis of (−)-microcarpalide from d-mannitol

The total synthesis of the actin-targeting metabolite (−)-microcarpalide is described. Ring-closing metathesis of a dienic ester was used as the key step. d-Mannitol was used as the chiral pool material for the construction of the olefinic acid moiety as well as the olefinic alcohol moiety of the molecule.     

A facile synthesis of a new trihydroxy piperidine derivative and (+)-proto-quercitol from d-(−)-quinic acid

We described herein the new synthesis of a trihydroxy piperidine derivative (1,4,5-trideoxy-1,5-imino-d-ribo-hexitol) and (+)-proto-quercitol from d-(−)-quinic acid, both are considered as inhibitors for glycosidases.     

Chiral self-assembly of triorganotin complexes: Syntheses, characterization, crystal structures and antitumor activity of organotin(IV) complexes containing (R)-(+)-methylsuccinic acid, (S)-(+)-methylglutaric acid and l-(−)-malic acid ligands

Six new chiral triorganotin(IV) complexes, {(R₃Sn)₂[C₃H₆(COO)₂]}_n (R = Me: 1; Bu: 2), {(R₃Sn)₂[C₄H₈(COO)₂]}_n (R = Me: 3; Bu: 4), and {(R₃Sn)₂[C₂H₄O(COO)₂]}_n (R = Me: 5; Bu: 6) have been prepared by treatment of (R)-(+)-methylsuccinic acid, (S)-(+)-methylglutaric acid and l-(−)-malic acid, with the corresponding R₃SnCl (R = Me, Bu) and sodium ethoxide in methanol. All the complexes were characterized by elemental analysis, FT-IR, NMR (¹H, ¹³C, ¹¹⁹Sn) spectroscopy and TGA. Except for 3, all of the complexes were also characterized by X-ray crystallography. The structural analyses reveal that complexes 1 and 5 have 2D network structures in which (R)-(+)-methylsuccinic acid and l-(−)-malic acid act as tetradentate ligands coordinated to trimethyltin(IV) ions. Complexes 2 and 4 have 3D metal-organic framework structures in which the deprotoned acids serve as tetradentate ligands. Complex 6 adopts a 1D zigzag chain structure and forms a 2D supramolecular framework through intermolecular C-H?O interactions. In addition, the antitumor activities of complexes 1-6 have been studied. We also have measured the specific rotation of the chiral dicarboxylic acids and the organotin derivatives.     

A general strategy for the stereoselective synthesis of l-1-deoxyallonojirimycin and d-1-deoxygulonojirimycin

A general strategy for the synthesis of deoxyazasugars from d-glucose is described. Ring-closing metathesis and stereoselective dihydroxylation reactions were used as key steps.     

Total synthesis of natural cis-3-hydroxy-l-proline from d-glucose

Synthesis of cis-3-hydroxy-l-proline from d-glucose is reported. The methodology involves conversion of d-glucose into N-benzyloxycarbonyl-γ-alkenyl amine which on 5-endo-trig-aminomercuration gave the pyrrolidine ring skeleton with sugar appendage in 25% yield. Alternatively, N-benzyloxycarbonyl-γ-alkenyl amine on hydroboration-oxidation, mesylation and intramolecular S_N2 cyclisation afforded pyrrolidine ring compound in high yield. Hydrolysis of 1,2-acetonide functionality, NaIO₄ cleavage followed by oxidation of an aldehyde into acid and hydrogenolysis afforded cis-3-hydroxy-l-proline in overall 29% yield from d-glucose.     

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.     

Total synthesis of (+)-epiquinamide from d-mannitol

The total synthesis of (+)-epiquinamide, a novel quinolizidine alkaloid isolated from the Ecuadoran poison frog, Epipedobates tricolor is described. The key step includes a ring-closing metathesis reaction to construct both the six member rings. d-Mannitol was used as a chiral pool material.     

One-pot inversion of d-mannono-1,4-lactone for the practical synthesis of l-ribose

l-Ribose was synthesized in a concise manner from d-mannono-1,4-lactone using one-pot inversion conditions. Treatment of d-mannono-1,4-lactone with piperidine, followed by mesylation-induced S_N2-type O-alkylation, afforded the desired one-pot inversion in an optimum yield, and the following straightforward transformations provided l-ribose in good yields.     

Stereoselective syntheses of (−)-chloramphenicol and (+)-thiamphenicol

Chloramphenicol and thiamphenicol have been enantioselectively synthesized using an asymmetric halohydrin reaction as a key step. In particular, halomethoxylation reaction was used, where O-methyl functions as a hydroxyl protecting group and eliminates an additional protection step.