Formal Syntheses of (±)‐Methylenomycins A and B

The syntheses of methyl ester of (±)‐desepoxy‐4,5‐didehydromethylenomycin A ( 4 ) and 2,3‐dimethyl‐5‐methoxycarbonyl‐2‐cyclopentenone ( 5 ) were accomplished from a common starting material, 2,3‐dimethyl‐4‐methoxyphenol (8), in only four and two steps in 35% and 53% overall yields, respectively. Photochemical rearrangements of masked p‐benzoquinones in methanol are the key steps.