Facile transformation of 2-azetidinones to unsaturated ketones: application to the formal synthesis of sphingosine and phytosphingosine

2-Azetidinones were smoothly transformed to unsaturated ketones through the ring opening of activated 2-azetidinone by phosphonate stabilized carbanion and subsequent Horner–Wadsworth–Emmons olefination of the resulting β-ketophosphonates with aldehydes. A formal synthesis of l-erythro-sphingosine and d-lyxo-phytosphingosine from readily available 2-azetidinone was established utilizing this methodology.