A concise and stereospecific synthesis of some cyclitols containing eight-membered rings: cyclooctane-1,2,3,4-tetraoles

Biological Properties of Cyclitols and Their Derivatives

Cyclitols are polyhydroxy cycloalkanes, each containing at least three hydroxyls attached to a different ring carbon atom. The most important cyclitol derivatives are inositols, quercitols, conduritols and pinitols, which form a group of naturally occurring polyhydric alcohols and are widely found in plants. In addition, synthetic production of cyclitols has gained importance in recent years. Cylitols are molecules synthesized in plants as a precaution against salt or water stress. They have important functions in cell functioning as they exhibit important properties such as membrane biogenesis, ion channel physiology, signal transduction, osmoregulation, phosphate storage, cell wall formation and antioxidant activity. The biological activities of these very important molecules, obtained both synthetically and from the extraction of plants, are described in this review.

Efficient synthesis of aziridinecyclooctanediol and 3-aminocyclooctanetriol

Cyclooctene endoperoxide was used as the key compound for the synthesis of aziridinecyclooctanediol and 3-aminocyclooctanetriol. Reduction of the cyclooctene endoperoxide, prepared by photooxygenation of cis,cis-1,3-cyclooctadiene, with zinc gave a cyclooctenediol and then benzylation of the hydroxy group yielded dibenzylated cyclooctene. Oxidation of the latter compound by OsO4/NMO followed by mesylation of the hydroxy group provided bis(benzyloxy)cyclooctane-1,2-diyl dimethanesulfonate. Reaction of the bis(benzyloxy)cyclooctane-1,2-diyl dimethanesulfonate with NaN3 gave 2-azido-3,8-bis(benzyloxy)cyclooctyl methanesulfonate. Reduction of the azide group and debenzylation to give an amine provided the new 3-aminocyclooctanetriol. Treatment of the 2-azido-3,8-bis(benzyloxy)cyclooctyl methanesulfonate with Zn/NH4Cl and debenzylation resulted in the target aziridinecyclooctanediol.

Efficient and regioselective synthesis of dihydroxy-substituted 2-aminocyclooctane-1-carboxylic acid and its bicyclic derivatives

The first synthesis of 2-amino-3,4-dihydroxycyclooctane-1-carboxylic acid, methyl 6-hydroxy-9-oxo-8-oxabicyclo[5.2.1]decan-10-yl)carbamate, and 10-amino-6-hydroxy-8-oxabicyclo[5.2.1]decan-9-one starting from cis-9-azabicyclo[6.2.0]dec-6-en-10-one is described. cis-9-Azabicyclo[6.2.0]dec-6-en-10-one was transformed into the corresponding amino ester and its protected amine. Oxidation of the double bond in the N-Boc-protected methyl 2-aminocyclooct-3-ene-1-carboxylate then delivered the targeted amino acid and its derivatives. Density-functional theory (DFT) computations were used to explain the reaction mechanism for the ring opening of the epoxide and the formation of five-membered lactones. The stereochemistry of the synthesized compounds was determined by 1D and 2D NMR spectroscopy. The configuration of methyl 6-hydroxy-9-oxo-8-oxabicyclo[5.2.1]decan-10-yl)carbamate was confirmed by X-ray diffraction.

Stereoselective syntheses of 3-aminocyclooctanetriols and halocyclooctanetriols

The efficient synthesis of two new stereoisomeric 3-aminocyclooctanetriols and their new halocyclitol derivatives starting from cis,cis-1,3-cyclooctadiene are reported. Reduction of cyclooctene endoperoxide, obtained by photooxygenation of cis,cis-1,3-cyclooctadiene, with zinc yielded a cyclooctene diol followed by acetylation of the hydroxy group, which gave dioldiacetate by OsO₄/NMO oxidation. The cyclooctane dioldiacetate prepared was converted to the corresponding cyclic sulfate via the formation of a cyclic sulfite in the presence of catalytic RuO₄. The reaction of this cyclic sulfate with a nucleophilic azide followed by the reduction of the azide group provided the target, 3-aminocyclooctanetriol. The second key compound, bromotriol, was prepared by epoxidation of the cyclooctenediol with m-chloroperbenzoic acid followed by hydrolysis with HBr(g) in methanol. Treatment of bromotriol with NaN₃ and the reduction of the azide group yielded the other desired 3-aminocyclooctanetriol. Hydrolysis of the epoxides with HCl(g) in methanol gave stereospecifically new chlorocyclooctanetriols.

An efficient synthesis of chloro-aminocyclooctanediol and aminocyclooctanetriol: an unexpected acetolysis product

A concise and efficient synthesis of 2-amino-4-chlorocyclooctanediol, aminocyclooctanetriols and unusual 1,3-hydride shift during the ring opening reaction of epoxide is described.

Continuous Endoperoxidation of Conjugated Dienes and Subsequent Rearrangements Leading to C-H Oxidized Synthons

We have investigated the continuous flow photooxidation of several conjugated dienes and subsequent rearrangement using a practical and safe continuous-flow homemade engineered setup. End-to-end approaches involving endoperoxidation, Kornblum-DeLaMare rearrangement, and additional rearrangements are comprehensively detailed with optimization, scope, and scale-up to obtain useful hydroxyenones, furans, and 1,4-dicarbonyl building blocks.

Ivorenolide B, an immunosuppressive 17-membered macrolide from Khaya ivorensis: structural determination and total synthesis

Ivorenolide B (1), an unprecedented 17-membered macrolide featuring conjugated acetylenic bonds and four chiral centers, was isolated from Khaya ivorensis. The structure of 1 was fully determined by spectroscopic analysis and total syntheses of its four most possible stereoisomers. Compound 1 showed significant immunosuppressive activity.

Antimicrobial action of an endophytic fungi from Sophor flavescens and structure identification of its active constituent

Endophytic fungus BS002 was isolated and characterized from Sophora flavescens by plate method, which has broad antimicrobial activity. Isolation and trace of a new bioactive compound from the fungus' culture extracts with the method of column chromatography and TLC biological autoradiography was conducted. Finally, it was identified as 6,7-(2'E) dibutenyl-5,8-dihydroxy-(Z)-cyclooct-2-ene-1,4-dione by nuclear magnetic resonance, infrared and liquid chromatography-mass spectrometry. The compound presented strong antifungal activities for example: Botryosphaeria berengriana f.sp. piricola, Physalospora piricola, Cladosporium cucumerinum Ell. Arthur., Fusarium oxysporum f.sp. cucumerinum, Fusarium moniliforme. The inhibition to Physalospora piricola was the strongest with an antibacterial diameter of 45 mm. This paper is the first report of the antimicrobial activity of endophytic fungi BS002 that was the secondary metabolites extracted from the seeds of Sophora flavescens. The results provide a broad foreground for biopharmaceuticals and biopesticide.

Ivorenolide A, an unprecedented immunosuppressive macrolide from Khaya ivorensis: structural elucidation and bioinspired total synthesis

Ivorenolide A (1), a novel 18-membered macrolide featuring conjugated acetylenic bonds and five chiral centers, was isolated from Khaya ivorensis. The structure of 1 was fully determined by spectroscopic analysis, single-crystal X-ray diffraction, and bioinspired total synthesis. Both compound 1 and its synthetic enantiomer 2 showed potent and selective immunosuppressive activity.

Design, synthesis, and biological activities of some branched carbasugars: construction of a substituted 6-oxabicyclo[3.2.1]nonane skeleton

Transformation of cyclohexa-2,4-diene-1,2-diylbis(methylene) diacetate to various carbasugars is described. Photooxygenation of a cyclohexadiene derivative gave a bicyclicendoperoxide, which was reduced with thiourea to [2-[(acetyloxy)methyl]cyclohexa-2,4-dien-1-yl]methyl acetate. Epoxidation of the remaining double bond followed by epoxide ring-opening and hydrolysis of the acetate groups gave one of the target hexols. The bicyclic endoperoxide was rearranged to a diepoxide with CoTPP. The diepoxide was reacted with sulfamic acid in acetic anhydride, resulting in the formation of a new branched carbasugar as well as in the formation of cyclitols with a 6-oxabicyclo[3.2.1]nonane skeleton. The mechanism of the formation of the products is discussed. The inhibition activity of six cyclitol derivatives was tested against α-glycosidase.

Synthesis of bishomoinositols and an entry for construction of a substituted 3-oxabicyclo[3.3.1]nonane skeleton

1,3,3a,7a-Tetrahydro-2-benzofuran was used as key compound for the synthesis of various bishomoinositol derivatives. The diene was subjected to an epoxidation reaction for further functionalization of the diene unit. The bisepoxide obtained was submitted to a ring-opening reaction with acid in the presence of water. Various bishomoinositols were synthesized. However, when the reaction was carried out in the presence of acetic anhydride, a substituted 3-oxabicyclo[3.3.1]nonane skeleton was formed. The mechanism of the formation of the products is discussed.