Cyclohexane polyols: Enantioselective synthesis of (+)-fortamine and of pseudosugars

Chemoselective Nozaki-Hiyama-Takai-Kishi and Grignard reaction: short synthesis of some carbahexopyranoses

A common, divergent, efficient, stereoselective and short approach for the total syntheses of some carbahexopyranoses namely, MK7607, (-)-gabosine A, (-)-conduritol E, (-)-conduritol F, 6a-carba-β-d-fructopyranose and other carbasugars using chemoselective Grignard or Nozaki-Hiyama-Takai-Kishi (NHTK) reactions and RCM. Herein, the Grignard and NHTK reactions are able to differentiate the reactivity difference between lactol or lactolacetate and aldehyde of 2 & 6 under given conditions to give the desired skeleton chemoselectivity.

Glycosylation of ent-kaurene derivatives and an evaluation of their cytotoxic activities

AIM

To discover more active and water-soluble derivatives of tetracyclic diterpenoids containing an exo-methylene cyclopentanone or an α-methylenelactone moiety.

METHODS

All of the key intermediates were synthesized from stevioside, and the target compounds were obtained through glycosylation of the 4-carboxyl group. The cytotoxicity of the target compounds against six human cancer cell lines, HepG2, Bel-7402, A549, U251, MCF-7 and MDA-MB-231, were evaluated by the MTT assay.

RESULTS

Compound 1b was more effective than the positive control adriamycin against the HepG2, Bel-7402, A549, MCF-7, and MDA-MB-231 cell lines with IC50 values of 0.12, 0.91, 0.35, 0.08, and 0.07 μmol·L(-1), respectively. Moreover, compound 3c exhibited the most potent and selective cytotoxic activity against the HepG2 cell line (IC50, 0.01 μmol·L(-1)).

CONCLUSION

Compounds 1b and 3c could be considered as potential anticancer candidates for further study.

Syntheses of carbocyclic analogues of α-D-glucosamine, α-D-mannose, α-D-mannuronic acid, β-L-idosamine, and β-L-gulose

A versatile synthesis of orthogonally protected derivatives of carba-α-D-glucosamine, carba-α-D-mannose, carba-α-D-mannuronic acid, carba-β-L-idosamine, and carba-β-L-gulose from methyl α-D-mannoside is described. Our synthetic strategy utilizes the palladium-promoted Ferrier carbocyclization and persistent butane-2,3-diacetal protection to produce a key chiral cyclohexanone intermediate, from which all five carbasugar derivatives can readily be obtained.

Facile syntheses of all possible diastereomers of conduritol and various derivatives of inositol stereoisomers in high enantiopurity from myo-inositol

Phosphoinositide-based signaling processes are crucially important in intracellular signal transduction events. Inositol phosphate analogues have been useful in probing the structure-activity relationships between inositol phosphates and biomacromolecules, and in studying biological functions of newly found inositol phosphates. Thus, a systematic and ready access to inositol stereoisomers is highly desirable. And practical and convenient syntheses of conduritols and related compounds are also important because of their biological activities and their synthetic utilities in the preparation of other bioactive molecules. We herein report the first syntheses of all possible diastereomers of conduritol and various derivatives of eight inositol stereoisomers in high enantiopurity from myo-inositol, which involve efficient enzymatic resolution of the intermediates conduritol B and C derivatives, followed by oxidation-reduction or the Mitsunobu reaction, and cis-dihydroxylation in stereo- and regioselective manners.

Facile synthetic routes to all possible enantiomeric pairs of conduritol stereoisomers via efficient enzymatic resolution of conduritol B and C derivatives

The first synthesis of all possible enantiomeric pairs of conduritol stereoisomers has been accomplished by efficient enzymatic resolution of conduritol B and C derivatives, followed by oxidation/reduction and the Mitsunobu reaction in stereo- and regioselective manners. Reaction: see text.

Novel and Efficient Insertions of Carbons Carrying O-, S-, and N-Linked Substituents: Synthesis of alpha-Alkoxyalkyl, alpha-(Alkylthio)alkyl, and alpha-(Carbazol-9-yl)alkyl Ketones

A wide variety of benzotriazolyl-stabilized anions 2, obtained by the lithiation of 1-(alpha-alkoxyalkyl)-, 1-[alpha-(alkylthio)alkyl]-, and 1-[alpha-(carbazol-9-yl)alkyl]benzotriazoles 1, on reaction with aliphatic and aromatic aldehydes and ketones, followed by rearrangement induced by heating in the presence of zinc bromide, furnish one-carbon-homologated alpha-alkoxyalkyl, alpha-(alkylthio)alkyl, and alpha-(carbazol-9-yl)alkyl ketones 4 in simple one-pot operations in good yields with excellent regioselectivity. In several alkoxymethylene insertions, intermediate 2-alkoxyoxiranes were separated in good yields, demonstrating the epoxide mechanism for the rearrangements and providing a facile approach to polysubstituted 2-alkoxyoxiranes, another class of important compounds.