Methoxide, aluminum boron

The epioxazoline is successively treated with chlorine, sodium iodide, cuprous oxide and boron trifluoride to produce the exomethylene compound (V). Methoxylation using chlorine with a methoxide followed by reaction with 1-methyl-lH-tetrazole-5-thiol and partial de-blocking using phosphorous pentachloride converts exomethylene (V) into the nucleus (VI). Acylation of the nucleus with an appropriately blocked side-chain (VII) followed by final de-blocking using aluminum chloride gives moxalactam acid (VIII). 

Cyclizatton Boron trifluoride etherate. Ion-exchange resin. Lithium, diethylamide. Mercuric acetate(then sodium borohydride). Methanesulfonic acid. Nickel carbonyl. Polyphosphate ester. Sodium aluminum chloride. Sodium methoxide. Trifluoracetic acid. 

Addition of dichlorocarbene, produced by treatment of ethyl tri-chloroacetate with sodium methoxide, to 3,4,6-tri-O-methyl-D-glucal gave, apparently, one product (gas-chromatographic analysis) in 82% yield. By stereochemical analogy with epoxidations, the product was considered to be l,5-anhydro-2-deoxy-l,2-C-(dichloromethylene)-3,4,6-tri-O-methyl-D-g/j/cero-D-ido-hexitol (21). Demethylation was brought about with boron trichloride at—70°, to give atriol from which a crystalline tribenzoate was obtained and reaction with lithium aluminum hydride caused reductive cleavage of the carbon-chlorine bonds.36 A similar addition was applied to 3,4-unsaturated furanosyl compound (see p. 247). 

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