4.6- dimethyl-2H-pyran-2-one

Anthracene undergoes photochemical [tt s + cycloaddition to yield the corresponding dimer. Similarly, photo-[4 - - 4]-dimerization of 4,6-dimethyl-2H-pyran-2-one gives a mixture of trans and cis adducts. This mixture on heating undergoes extrusion of carbon dioxide to give (1Z,3Z,5Z,7Z)-l,3,5,7-tetramethylcycloocta-l,3,5,7-tetraene (Scheme 4.26). 

P-d-Glucopyranosyloxy) -5,6-dihydro-4,6-dimethyl-2H-pyran-2-one. 4-P-d-Glucopyranosyloxy-3-methyl-2-hexen-5-olide... 

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