Straightforward Enantioselective Access to γ‑Butyrolactones Bearing an All-Carbon β‑Quaternary Stereocenter

An enantioselective one-pot aldol/lactonization sequence has been developed to access highly challenging γ-butyrolactones bearing an all-carbon quaternary stereocenter at the β-position by reacting acylated succinic esters with aqueous formaldehyde in the presence of 3 mol % loading of a cinchona alkaloid-derived squaramide providing direct access to paraconic acid derivatives in high yield and fairly good level of enantioselectivity (up to 88% ee).