carbonic acid allyl ester 6-(tert-butyl-dimethyl-silanyloxy)-17-ethyl-19-(6-hydroxy-3-methyl-3,6-dihydro-2H-pyran-2-yl)-3,5,7,11,15-pentamethyl-8-oxo-9-triisopropylsilanyloxymethyl-nonadeca-2,10,12,16,18-pentaenyl ester