Alkylation of Enamines of Bis(ethy1thio)acetaldehyde : Synthesis of Norpyrenophorin ... By GORDON S BATES* and S RAMASWAMY (Department of Chemzstry, Unzverszty of Brztzsh Columbza, Vancouvev, B C , Canada V6T 1Y6) ... Summary Alkylation of the potassium anion of the AN important structural feature of many natural products ... (e g cytochalasin A, and the diolides pyrenophorin, nor- pyrenophorin, and vermiculin) is the presence of a d-oxoalk- ...