A short and concise synthesis of isofagomine, homoisofagomine, and 5′-deoxyisofagomine

A short and concise synthesis of isofagomine derivatives via the epoxidation of chiral N-Boc-5-hydroxy-3-piperidene, followed by regioselective epoxide ring opening is described. This constitutes the first reported synthesis of homoisofagomine and the 5′-deoxyisofagomine.     

Improved Ritter reaction with CF3-containing oxirane for an access to central units of protease inhibitors

The influence of fluorinated alcohols on the BF₃·Et₂O-promoted Ritter type reaction has been investigated. Trifluoroethanol/BF₃·Et₂O system allowed access to the central unit of protease inhibitors by the ring opening of fluorinated epoxide 2 with various nitriles.     

Ring-expanded analogues of natural oxetanocin

Synthesis of ring-expanded analogs of the natural compound, oxetanocin is described. The starting material for the synthesis of the series, 4-7, was d-glucosamine and introduction of the base moiety was done through the stereochemically appropriate epoxide. For the enantiomeric series, 8-11, the starting material was d-glucose and preparation of the key intermediate involved a rearrangement reaction. The structures of the target molecules were established by NMR, HRMS, optical rotation and UV data. Single-crystal X-ray data confirmed the enantiomeric structural assignments.     

Synthesis and structure of an air-stable bis(pentamethylcyclopentadienyl) zirconium pentafluorbezenesulfonate and its application in catalytic epoxide ring-opening reactions

An air-stable mononuclear complex of bis(pentamethylcyclopentadienyl) zirconium pentafluorbezenesulfonate was successfully synthesized by treating C₆F₅SO₃Ag with [(CH₃)₅Cp]₂ZrCl₂, which showed the cationic uninuclear structure of [{(CH₃)₅Cp}₂Zr(CH₃CN)₂(H₂O)][OSO₂C₆F₅]₂·CH₃CN (1) confirmed by the X-ray analysis. Complex 1 was also characterized by other techniques and found to have the good nature of air-stability, water tolerance, thermally-stability and strong Lewis-acidity. Moreover, the complex showed high catalytic activity and recyclability in catalytic epoxide ring-opening reactions by amines or alcohols. This catalytic system affords a simple and efficient approach for synthesis of β-amino alcohols or β-alkoxy alcohols.     

Synthesis and rearrangement reactions of 1,4-dihydrospiro[1,4-methanonaphthalene-9,1′-cyclopropane] derivatives

Reactions of benzyne with ester derivatives of spiro[2.4]hepta-4,6-dien-1-ylmethanol were performed. By rearrangement reaction of cyclopropyl methanol units of ((1s*,1′R*,2R*,4′S*)-1′,4′-dihydrospiro[cyclopropane-1,9'-[1,4]methanonaphthalen]-2-yl) methyl 3,5-dinitrobenzoate (13) and its isomer (14), corresponding allyl chlorides were obtained. Two rearrangement products were obtained from bromination of compound 13 with an equivalent amount of Br₂. A naphthalene derivative including allyl and CHO moiety was formed for reactions from compounds with epoxide of 13 and 14 with NaN₃ by sequential rearrangements. Formations of products are discussed.     

Synthesis of bavachromanol from resorcinol via a tandem cationic cascade/EAS sequence

The natural chalcone bavachromanol has been prepared through a tandem reaction sequence that joins cationic cyclization of an epoxide to an adjacent MOM-acetal with electrophilic aromatic substitution by a presumed methoxymethylene cation. Only a single regioisomer of the tandem product was observed, with substitution taking place exclusively ortho to the position of the original acetal. This regiocontrol provided a key intermediate from a symmetrical precursor, and allowed preparation of the meroterpenoid through a short reaction sequence.     

Allylation of epoxides with allylic indium reagents

Allylindium sesquihalide reacts with epoxide to give homoallyl alcohol via a 1,2-shift reaction. In contrast, allylindate gives the ring-opening product without rearrangement.     

Highly active double metal cyanide complexes： Effect of central metal and ligand on reaction of epoxide/CO2

Various novel double metal cyanide (DMC) catalysts were successfully prepared by modifying the central metal (M) and one of cyanide ion (CN-) in Zna[M(CN)b]c complex. Such modifications have significant impact on the catalytic efficiency as well as the polymer selectivity for the reaction of PO/CO2. Zn–Ni(Ⅱ) DMC is a potential catalyst for alternating copolymerization of PO/CO2, and DMC catalysts based on Zn3[Co(CN)5X]2 (X = Br-and N3-) exhibit moderate efficiency for the production of polycarbonates. This research presents the preliminary exploration of novel DMC complex via chemical modification of its central metal and ligand.     

Acid-catalysed oxidative ring-opening of epoxide by DMSO. Theoretical investigation of the effect of acid catalysts and substituents

DFT studies have been carried out in order to investigate the reaction mechanism of a series of acid-catalysed oxidative ring-opening of epoxides in DMSO. The role of the acid catalyst during the oxidation of ethylene oxide has been investigated by employing three acids, namely H₃O⁺, Li⁺, and Mg²⁺. Effects of substituents on the epoxide have been investigated by including butene oxide and cyclopentene oxide as the reacting species. Stationary points have been obtained at the B3LYP/6–31++G(d,p) level of theory and the reaction barriers have been evaluated through free-energy calculations. This is the first mechanistic elucidation for such a process, involving oxidation of the epoxide ring by DMSO. The mechanism proceeds in two steps, namely a ring-opening step followed by an intramolecular proton transfer which leads to an -hydroxyketol. The results show that the second step is the energetically less favourable, a feature consistent with the harsh experimental conditions needed to obtain such products. The role of the acid catalyst is discussed and we show that use of H₃O⁺ or Mg²⁺ as an activator leads to similar results concerning the reaction energetics.Proceedings of the 11th International Congress of Quantum Chemistry satellite meeting in honor of Jean-Louis Rivail     

Studies on the synthesis of DNA-damaging part of leinamycin: regioselectivity in Ti(OiPr)4 mediated opening of hydroxy epoxides with carboxylic acids

The preparation of the key intermediate in the synthesis of the DNA damaging fragment of the anticancer antibiotic leinamycin starting from geraniol is described. The synthetic sequence involves the building of a quaternary asymmetric center through kinetic resolution through Sharpless epoxidation followed by the regioselective opening of the resultant enantiomerically pure hydroxyepoxide and intramolecular Wittig-Horner olefination.