Concise synthesis of ricciocarpin A and discovery of a more potent analogue

Cascade reactions enable the rapid build-up of molecular complexity from relatively simple starting materials. Both rapid construction and the ability to prepare related structures are crucial to the study of biological activities. Here, we report an efficient, highly enantioselective and diastereoselective total synthesis of ricciocarpin A. The key feature of the synthesis is a one-pot, three-step, organocatalytic reductive Michael–Tishchenko cascade. The conciseness and flexibility of this approach not only resulted in the synthesis of the natural product, but also of its antipode and four other structural analogues. A preliminary biological evaluation of these compounds identified an analogue with significantly improved molluscicidal activity

The Proline-Catalyzed Double Mannich Reaction of Acetaldehyde with N-Boc Imines

Double‐cross: Proline catalyzes the double Mannich reaction of acetaldehyde with N‐Boc imines in excellent yields (up to 99 %; Boc=tert‐butoxycarbonyl) and close to perfect diastereo‐ and enantioselectivities. Depending on the choice of catalysts, both the chiral, pseudo‐C2‐symmetric diastereomer and the corresponding meso compound can be prepared. Cross double Mannich reactions of acetaldehyde with two different imines are also demonstrated

The Catalytic Asymmetric Knoevenagel Condensation

116 years after the discovery of the Knoevenagel condensation, the first catalytic asymmetric variant has been developed. Dynamic kinetic resolution in the reaction of α‐branched aldehydes with malonates in the presence of a newly designed and readily available modified cinchona amine catalyst gives the corresponding alkylidene malonates in high enantioselectivity (see scheme)