Total synthesis of preaurovertin, putative biogenetic precursor of aurovertin. Biosynthetic interrelationships between the aurovertins, citreoviridinols and asteltoxin

A number of complementary biomimetic approaches to the tetrahydrofuranyl portion of the dienal 13, which was used in a synthesis of preaurovertin, are described. Epoxidation of the trienoate 31 produces largely the β-epoxide 32, which on treatment with aqueous trifluoroacetic acid undergoes deacetalisation and concomitant cyclisation leading to compound 34. After conversion of 34 into dienal 13, a Wittig reaction with the ylide derived from the phosphonium salt 37 produces preaurovertin.