Sequential dialkylation of methoxypropadiene via the corresponding lithium derivatives gives 1, 3-dialkylated methoxyallenes which undergo acid-catalysed ring closure to 1, 7- dioxaspiro [5.5] undec-4-enes; by this route (6S*, 9S*)-9-ethyl-1, 7-dioxaspiro [5.5] undec-4- ene (15b) has been prepared which has previously been converted into talaromycins A and B.
