A novel 7, 9, 11-trimethyl-8,10,12-trioxatetracyclo[5.3.2.0. 4 , 9 .0 4 , 1 1 ]-dodecl-yl]-2 -butanone skeleton 3 has been synthesized by the treatment of 2-acetyl-3,4-dihydro-2,5-di 3 -oxo-butyl)-6-methyl-(2H)-pyran 2, with H-ZSM-5. However, the treatment of compound 2 with p-TsOH gives bibenzyls. Present report provides a unique acid catalysed cyclization of diketo-olefin system over zeolite, X-ray crystal structure of 3 is also presented.