SYNTHESIS OF (+/-)-3-AMINO-2,4-DIHYDROXY-6-HYDROXYMETHYL-8-OXABICYCLOOCTANE DERIVATIVES, AND THEIR ANHYDRO-RING-MIGRATION WITH HYDROGEN BROMIDE-ACETIC ACID

Article abstract of DOI:10.1016/0008-6215(89)85011-6

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 (4a-6a) of (+/-)-2,4-dihydroxy-6-hydroxymethyl-3-nitro-8-oxabicyclo<3.2.1>octane in 52percent combined yield.Their structures were assigned on the basis of ¹H-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 (4c-6c), treatment of which with 15percent hydrogen bromide-acetic acid at 80 deg replaced the primary acetoxyl group with bromine, giving the monobromo derivatives 4d-6d.Migration of the anhydro rings also occurred with 4c and 6c, yielding the respective isomers (1RS,2RS,4SR,5RS,6RS,7SR)-7-acetamido-2,6-diacetoxy-4-bromomethyl-8-oxabicyclo<3.2.1>octane (7) and (1RS,2RS,4SR,5RS,6SR,7SR)-6-acetamido-4,7-diacetoxy-2-bromomethyl-8-oxabicyclo<3.2.1>octane (8a).The mechanism of these reactions is considered.