title: Useful access to enantiomerically pure protected inositols from carbohydrates: the aldohexos-5-uloses route.
abstract: The intramolecular aldol condensation of aldohexos-5-ulose derivatives of the D-xyloand L-ribostereoseries has been studied. Only one of the four possible inososes was isolated from both stereoseries in reasonable yields (30-38%). The results obtained, together with the previous findings for the L-arabinoand L-lyxostereoseries, allowed for the rationalisation of a mechanism of the reaction based on open-transition-state models and electron-withdrawing inductive effects. Complementary reductions of the intermediate inososes were possible by changing the reaction conditions, and two isomeric inositol derivatives were obtained with complete stereoselection from each inosose. The presented approach permits us to control the configuration of three out of the six stereocentres of the inositol frame and gives access to seven of the nine inositols. Noteworthy, for the D-xyloderivative, the two-step sequence (condensation followed by reduction with NaBH(OAc)3) represents the biomimetic synthesis ofmyo-inositol. Furthermore, the sugar-based pathway leads directly to enantiomerically pure selectively protected inositols and does not require any desymmetrisation procedure which is needed whenmyo-inositol and other achiral precursors are employed as starting materials. As an example of application of the method, the indirect selective protection of secondary inositols' hydroxy functions, by placing specific protecting groups on the aldohexos-5-ulose precursor has been presented.
authors.affiliation: Università di Pisa, Dipartimento di Farmacia, Via Bonanno 33, 56126 Pisa, Italy.
authors.forename: Felicia
authors.initials: F
authors.lastname: D'Andrea
authors.affiliation: Università di Pisa, Dipartimento di Farmacia, Via Bonanno 33, 56126 Pisa, Italy.
authors.forename: Giorgio
authors.initials: G
authors.lastname: Catelani
authors.affiliation: Università di Pisa, Dipartimento di Farmacia, Via Bonanno 33, 56126 Pisa, Italy.
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Guazzelli
authors.affiliation: Università di Catania, Dipartimento di Scienze del Farmaco, Viale A. Doria 6, 95125 Catania, Italy.
authors.forename: Venerando
authors.initials: V
authors.lastname: Pistarà
keywords: aldohexos-5-uloses; inositols; intramolecular aldol condensation; stereoselective hydride reduction