Synthesis of (±)-3-amino-2,4-dihydroxy-6-hydroxymethyl-8-oxabicyclo[3.2.1]octane derivatives, and their anhydroring-migration with hydrogen bromide-acetic acid

✍ Scribed by Seiichiro Ogawa; Masaru Orihara

• Book ID: 102990152
• Publisher: Elsevier Science
• Year: 1989
• Tongue: English
• Weight: 605 KB
• Volume: 194
• Category: Article
• ISSN: 0008-6215
• DOI: 10.1016/0008-6215(89)85011-6

✦ Synopsis

Nitromethane-mediated cyclization of the dialdehyde generated by periodate oxidation of (+)-2exo,3exo-dihydroxy-5endo-hydroxymethyl-7-oxabicyclo[2.2.1]heptane (2) in methanolic sodium methoxide afforded, after neutralisation, three diastereoisomers (4.a-6a) of (f )-2,4-dihydroxy-&hydroxymethyl-3-nitro-8-oxabicyclo[3.2.l]octane in 52% combined yield. Their structures were assigned on the basis of *H-n.m.r. spectra of the respective triacetates (4b-6b). Hydrogenation of the nitro compounds in methanol-acetic anhydride with Raney nickel followed by acetylation gave the corresponding N-acetyl derivatives (4&c), treatment of which with 15% hydrogen bromide-acetic acid at 80" replaced the primary acetoxyl group with bromine, giving the monobromo derivatives 4d-6d. Migration of the anhydro rings also occurred with 4c and 6e, yielding the respective isomers (lRS,2RS,4SR, SRS,6RS,7SR)-7-acetamido-2,6-diacetoxy-4-bromomethyl-8-oxabicyclo[3.2,l]octane ( 7) and (lRS,2RS,4SR,5RS,6SR,7SR)d-acetamido-4,7-diacetoxy-2-bromomethyl-8-oxabicyclo[3.2.l]octane @a). The mechanism of these reactions is considered.