Total Synthesis of - 9S -Dihydroerythronolide

Stork s synthesis of dihydroerythronolide A illustrates the usefulness of the butenolide template route to polypropionate sequences. 

The dihydroxyfuranone 78 was transformed into the butenolide 79, illustrating the hydroxybutenolide approach to such a compound. After rhodium catalyzed hydrogenation, a second hydroxybutenolide homologation gave the 

---

Crimmins s TiCL -mediated asymmetric aldol condensation protocol was used in the enantioselective total synthesis of (9S)-dihydroerythronolide A (68)25 (Scheme 2.lx). Swern oxidation of the primary alcohol 69 provided the aldehyde 70 in almost quantitative yield, which underwent asymmetric aldol condensation with the titanium enolate of (A )-4-bcnzyl-3-propionyloxa/,olidin-2-onc (26M) in the presence of (-)-sparteine to afford the aldol adduct desired (71) as a single diastereomer. 

---