Bromination of sugar enones and enonolactones

✍ Scribed by Christían Di Nardo; Oscar Varela; Rosa M. de Lederkremer; Ricardo F. Baggio; Daniel R. Vega; María T. Garland

• Book ID: 102996316
• Publisher: Elsevier Science
• Year: 1995
• Tongue: English
• Weight: 564 KB
• Volume: 269
• Category: Article
• ISSN: 0008-6215
• DOI: 10.1016/0008-6215(94)00352-g

✦ Synopsis

Bromination of 2,

4,

(1) took place diastereoselectively to afford a single product: 2,4,6-tri-O-benzoyl-2,3-dibromo-3-deoxy-D-altrono-l,5-1actone (2). The configuration of C-2 and C-3 was determined as R,R by NMR spectroscopy and taking into account considerations of the stereochemical course of the bromination. The configuration of 2 was confirmed by X-ray analysis, which also revealed that the conformation of the lactone ring consists of a 4Ha(D) distorted half-chair. The bromine addition to 2, 5,6,7-tetra-O-benzoyl-D-arabino-hept-2-enono-l,4-1actone (5), readily prepared by DBU-promoted elimination from the perbenzoylated lactone derivative 4, was also diastereoselective and led to the dibromo derivative 6, whose configuration for C-2 and C-3 was assigned as S,S. Bromination of the a,/3-unsaturated carbonyl system of 2-propyl 6-O-acetyl-3,4-dideoxy-ot-Dglycero-hex-3-enopyranosid-2-ulose (7) afforded an unsaturated monobromo derivative: 2-propyl 6- O-acetyl-3-bromo-3,4-dideoxy-a-D-glycero-hex-3-enopyranosid-2-ulose (8), suggesting that dehydrobromination occurred after addition of bromine.