title: A new and efficient entry to D-xylo-hexos-4-ulose and some derivatives thereof through epoxidation of the 3,4-hexeno derivative of diacetone-D-glucose.
abstract: A new preparation of D-xylo-hexos-4-ulose (1) and of its 3-m-chlorobenzoate (2) has been devised using the epoxidation of 3-deoxy-1,2:5,6-di-O-isopropylidene-D-erythro-hex-3-enofuranose (6) as the key step. The epoxidation of 6 in CH2Cl2 furnished with high yield 1,2:5,6-di-O-isopropylidene-3-O-m-chlorobenzoyl-4-C-hydroxy-D-xylo-hexos-4-ulo-1,4-furanose as a mixture of C-4 hemiacetal anomers (7a,b), which, on acid hydrolysis, gave a tautomeric mixture of 3-O-m-chlorobenzoyl-D-xylo-hexos-4-ulose (2) with an overall 60% yield from 6. The formation of 4-C-methoxy-diacetone-D-glucose derivatives (11a,b) through epoxidation-methanolysis of 6, took place with reduced yield because of the competition between m-chlorobenzoic acid (MCBA) and methanol to the opening by attack at C-4 of the intermediate epoxide and the formation of acyclic products arising from the alternative nucleophilic attack at C-1. Acid hydrolysis of derivatives 11 gave D-xylo-hexos-4-ulose (1) with a 35% overall yield from 6. NMR analysis showed that 2 is composed, in CD3CN, mainly by a 7:3 mixture of 4-keto-alpha- and beta-pyranose forms, while 1, in D2O, is present as a more complex mixture constituted mainly by 4-keto-alpha- and beta-pyranoses and their respective hydrates in a 17:15:34:34 ratio.
authors.affiliation: Dipartimento di Chimica Bioorganica e Biofarmacia, Università di Pisa, Via Bonanno, 33, I-56126 Pisa, Italy.
authors.forename: Emanuele
authors.initials: E
authors.lastname: Attolino
authors.forename: Giorgio
authors.initials: G
authors.lastname: Catelani
authors.forename: Felicia
authors.initials: F
authors.lastname: D'Andrea
authors.forename: Martina
authors.initials: M
authors.lastname: Landi
mesh_terms: D000096:Acetone; D002723:Chlorobenzoates; D004149:Dioxoles / Q000138:chemical synthesis*; D004852:Epoxy Compounds; D005947:Glucose / Q000031:analogs & derivatives* / Q000737:chemistry; D006601:Hexoses / Q000138:chemical synthesis*; D013013:Sorbose / Q000031:analogs & derivatives*; D014994:Xylose
chemical_list: C515043:1,2-5,6-di-O-isopropylidene-3-deoxyhex-3-enofuranose; C515042:4-ketoglucose; D002723:Chlorobenzoates; D004149:Dioxoles; D004852:Epoxy Compounds; D006601:Hexoses; D000096:Acetone; C013686:sorbosone; D014994:Xylose; D005947:Glucose; D013013:Sorbose