合成路线1

The addition of 2-(trimethylsilyl)ethylmercaptane (I) to 2,4-hexadiyn-1,6-diol (II) catalyzed by KOH in DMF gives the addition product (III), which is oxidized with Dess-Martin periodinane in dichloromethane or oxalyl chloride in DMSO yielding the dialdehyde (IV). The condensation of (IV) with tetrabromomethane by means of triphenylphosphine in dichloromethane affords the tetrabromo derivative (V), which is treated with butyllithium in THF to give the diacetylenic dianion (VI). The reaction of (V) with methyl iodide yields the mono methylated compound (VII), which is condensed with cis-1,2-dichloroethylene (VIII) by means of Pd(PPh3)4/CuI/butylamine in benzene affording the cis-chlorovinyl compound (IX). THe reaction of (IX) with vinylmagnesium bromide (X) catalyzed by Pd(PPh3)4 in benzene gives precursor (XI), which is finally submitted to an oxidative cyclization by means of tetrabutylammonium fluoride/trifluoroacetic acid and iodine.