“…The unpurified aldehyde was directly subjected to a Horner−Wadsworth−Emmons homologation with the required phosphonate reagent to give the α,β-unsaturated ketone 12 in 90% isolated yield ( E : Z > 95:05) over the two-step sequence . Selective hydrogenation of the double bond proceeded smoothly, leaving the PMB group intact to give the corresponding methyl ketone, which, after treatment with N,N -dimethyl hydrazine in the presence of TMSCl as a dehydrating agent, gave the corresponding hydrazone 13 (18 S ,19 R ) in 87% yield for the two-step sequence . Starting from oxazolidinone ( S )- 8 , we were able to prepare hydrazone 14 (18 R ,19 S ), with the intention of preparing the initially proposed spiroketal of spirofungin B (see Scheme ).…”