合成路线1

The precursor cis-cinnamate (XXXIX) can be obtained by several synthetic routes. Bromination of ethyl trans-4-methoxycinnamate (I) afforded the dibromo ester (XXXVI), which underwent dehydrohalogenation and hydrolysis to the arylpropiolic acid (XXXVII) upon treatment with ethanolic KOH. Acid (XXXVII) was converted to the corresponding isopropyl ester (XXXVIII) by DCC-mediated coupling with isopropanol. Semihydrogenation of (XXXVIII) in the presence of Lindlar catalyst led to the required cis cinnamate (XXXIX). Alternatively, anisaldehyde (X) was converted to the gem-dibromostyrene (XL) by condensation with CBr4 in the presence of PPh3. Reaction of (XL) with BuLi, followed by addition of isopropyl chloroformate to the resultant lithium acetylide, furnished the arylpropiolate (XXXVIII). In another method to obtain the cis-cinnamate (XXXIX), trans-4-methoxycinnamic acid (XLI) was converted to the isopropyl ester (XLII), which was then photochemically isomerized to the desired cis-cinnamate (XXXIX)