Wiley InterScience Backfile Collection 1832-2000
Chemistry and Pharmacology
Methyl (E)-5-bromo-4-oxo-2-pentenoate (6) and the corresponding oxime 5 were prepared in high yields by starting from methyl levulinate (3). The novel nitrosoalkene 8, generated in situ from oxime 5, smoothly added to silyl enol ether 7 to give 1,2-oxazine 9 and nitrone 10 as byproduct. Methods are described transforming intermediate 9 into unsaturated diketo ester 11, or oximes 13, 15, and 18, which may serve as precursors of pyrenophorin. Reductive ring cleavage of 1,2-oxazine 9 with Raney nickel efficiently afforded the saturated diketo ester 19. Its intramolecular aldol reaction gave cyclopentenone derivative 20, which is a known precursor of (Z)-jasmone. Cycloaddition of methyl α-nitrosoacrylate to silyl enol ether 22 provided 1,2-oxazine 23. This compound was directly converted into the ant-trail pheromone 24 by hexacarbonylmolybdenum-promoted ring contraction.
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