Heliopsis helianthoides

When 2-bromo-4,5-methylenedioxyphenylpropiolic acid (IM) failed, on heating with acetic anhydride, to yield the desired intramolecular cyclized anhydride (107). the problem was overcome by the use of dicyclohexylcarbodiimide in dimethoxy-ethane solution below 0° (99,100). The product 11071 was subsequently used (101,102) as an intermediate for the synthesis of helioxanthin 11081 IScheme 20) which had been isolated and identified as a constituent of Heliopsis helianthoides (103,104),... 

---