Salvatore Pollicino

A General Procedure to Enantiopure Conduritols: Sulfur-Mediated Synthesis of (+)-Conduritol B and (−)-Conduritol F Derivatives and of (−)-Conduritol E and F

Abstract We have demonstrated the generality of a simple procedure, synthesizing enantiomerically pure (+)-conduritol B and (−)-conduritol F derivatives, starting from d -mannitol and d -sorbitol, respectively. This method, slightly modified, can also be applied to the synthesis of unprotected conduritols: (−)-conduritol E and (−)-conduritol F were obtained.

New simple and inexpensive synthetic route, mediated by sulfur, to enantiopure (−)-conduritol E derivative from D-mannitol

Abstract We have synthesized a (−)-Conduritol E derivative, enantiomerically pure, using as starting material D-mannitol. This latter, possessing already the same configuration of the expected product at the four chiral carbon atoms, was subjected to reaction to form a cyclic unsaturated polyhydroxylated compound, preserving the configuration at all chiral carbon atoms of the sugar.

Synthesis and glycosidase inhibition of new enantiopure 2,3-diamino conduritols

Abstract A new 2,3-diamino conduritol, isoster of conduritol F, was obtained starting from d -sorbitol. In the synthetic sequence an unprecedented transannular cyclization led, as a side product, to a bicyclic compound bearing a cyclopropyl ring. The synthesis of the completely deprotected 2,3-diamino conduritol, isoster of conduritol B, was devised via the intermediate O-benzylation of the OH groups. The O-methylated and deprotected 2,3-diamino conduritols were evaluated as inhibitors of α- and β-glucosidase.

Stereoselective addition of organomanganese reagents to chiral acylsilanes and aldehydes

Organomanganese halides and organomanganates prepared by transmetalation of organolithium and Grignard reagents add smoothly to the carbonyl moiety of acylsilanes and of substituted aldehydes bearing a chiral center at the a-position affording the desired alcohols in good to excellent yields and with essentially no undesired products from enolization. Comparison of the stereochemical outcome with that observed for other organometallic species, outlines the capability of organomanganese reagents to induce uniformly good diastereoselectivities, in a number of cases significantly higher than reported previously for these reactions. The key role displayed by the R3Si group in promoting high 1,2-asymmetric induction, clearly emerges in the comparison of acylsilane 12 with the corresponding aldehyde 13. The sense of the Cram:anti-Cram selectivity depends upon the nature of the carbonyl reagents engaged in these reactions.

Alkyllithium-promoted ring fissions of halides derived from 1,4:3,6-dianhydrohexitols

Abstract Halogen-substituted 2,6-dioxabicyclo[3.3.0]octanes, readily obtained from 1,4:3,6-dianhydro-D-mannitol may be useful sources of highly functionalized homochiral synthons. Treated with an alkyllithium the title compounds undergo dehalogenative (X = I) or nondehalogenative ring fission (X = Cl) giving homochiral 2,5-dihydrofurans or 2-(1-halogenovinyl)tetrahydrofurans, respectively. The two elimination processes compete comparably for X = Br.

Synthesis and biological activity of the (−)-(2R,3S,4S)-3-azido-4-methoxy-2-(1′S-methoxy-2′-azido)ethyl-thiolane

Abstract A stereospecific ring contraction reaction, promoted by NaN3, was detected starting from a thiepane derivative obtained from d -sorbitol, an inexpensive alcohol sugar. The major polyfunctionalized thiolane derivative obtained was investigated as a potential glycosidase inhibitor.

Formation of cyclic sulfonium salts by Me3SiI-promoted intramolecular displacement of hydroxide or methoxide by sulfide. Ring contraction thiepane → thiolane

Abstract A suitably positioned (1, 2-, 1, 4-, and 1, 5-) intramolecular sulfide interferes with the iodotrimethylsilane-promoted iodine for hydroxyl substitution, as well as the related alcohol deprotection procedure (regioselective cleavage of methyl ethers). The outcome may be a cyclic sulfonium salt or an iodide arising from cleavage of a sulfonium intermediate. Cyclization is especially favored with secondary and tertiary alcohols or ethers, and with an aliphatic more than an aromatic sulfide function. A transannular version of the reaction results in the facile ring contraction of a 7- to a 5-membered cyclic sulfide. The trimethyliodosilane-promoted iodine for hydroxyl substitution, as well as the related methyl ether cleavage reaction, fail for substrates where a sulfide function is suitably positioned relative to the oxygen function. The outcome may be either a cyclic sul fonium iodide or a rearranged sulfide arising from cleavage of a sulfonium intermediate as in the case of 4-methoxy thiepane Download : Download full-size image

Synthesis of new enantiopure thiepane derivatives and their evaluation as glycosidase inhibitors

Starting from inexpensive alcohol sugars we have synthesised a series of oxygen- and nitrogen-containing enantiopure thiepanes to investigate the structural and stereochemical requirements for inhibitory activity against a variety of glycosidases. An interesting trend was observed on analysis of the biological screening results for these derivatives.

Organothiosilanes in the synthesis of functionalized benzothiophenes and benzofurans

Fluoride-ion-induced reactivity of bromo(phenylthio)methyltrimethylsilane with o-hydroxy benzaldehyde and o-mercaptobenzyl alcohol afforded direct and simple access to 2,3-dihydro-2-phenylthio-3-hydroxybenzofuran and 2-phenylthio-3-hydroxy-2,3-dihydrobenzothiophene, respectively. 2-Phenoxy-3-hydroxy-2,3-dihydrobenzo-thiophene could be similarly obtained through a slightly modified procedure.

Low Pressure Hydrogenation of Unsaturated Sulphides with Homogeneous and Heterogeneous Ruthenium Catalysts

Abstract Ru2O-nH2O and [Ru3O(AcO)6(H2O)3j+AcO-were examined for catalytic activity in the hydrogenation of a series of unsaturated sulphides under heterogeneous and homogeneous conditions, respectively. By the appropriate combination of these two methodologies, a number of saturated sulphides could be synthesized in satisfactory to good yields, thus minimizing side reactions.