Manuela Mariani

Intramolecular aldol cyclization of L-lyxo-hexos-5-ulose derivatives: a new diastereoselective synthesis of D-chiro-inositol.

Abstract The DBU-promoted intramolecular aldol condensation of two partially protected l - lyxo -hexos-5-ulose derivatives ( 8 and 9 ), in turn obtained starting from methyl β- d -galactopyranoside, takes place with fairly good yield and complete diastereoselectivity to give 2 l -(2,3,6/4,5)-pentahydroxycyclohexanone derivatives, 10 and 11 . The stereoselective reduction of inosose 10 with sodium triacetoxyborohydride leads, after catalytic debenzylation, to d - chiro -inositol ( 1 ), while the sodium borohydride reduction furnishes, with opposite stereoselectivity, a derivative of allo -inositol.

Concise synthesis of 1-deoxy-4-O-β-d-galactopyranosyl-d-nojirimycin avoiding a glycosylation step ☆ ☆☆

Abstract 2′,6′-Di- O -benzyl-2,3:5,6:3′,4′-tri- O -isopropylidenelactose dimethyl acetal was used as starting material for the preparation of the until now unknown 4- O -β- d -galactopyranosyl- d - xylo -hexos-5-ulose derivatives 7 – 9 , through selective C-5 oxidation of its partially deprotected derivatives 4 – 6 . Hydrolysis of 7 – 9 with aq. CF 3 COOH led to deprotected 1,5-dicarbonyl disaccharides 11 – 12 , diastereoselectively transformed without purification into 1-deoxy-4- O -β- d -galactopyranosyl- d -nojirimycin derivatives in about 60% yield, through a double reductive amination reaction.