Alkylation and Reductive Decyanation of 4-Cyano-2,2-dimethyl-1,3-dioxanes (Cyanohydrin Acetonides)

Preparation of β-Hydroxyketones (Aldols) from the Alkylation of O-Silyl Aryl Cyanohydrins with Epoxides

β-Hydroxyketones (aldols) are prepared from the alkylation-deprotection of O-silylated aryl cyanohydrins with epoxides. Key to the success of the method was the suppression of an in situ cyclic imidate formation that occurs upon initial opening of the epoxide ring.

Total synthesis of lepadiformine alkaloids using N-Boc α-amino nitriles as trianion synthons

Lepadiformine A, B, and C were synthesized in an enantiomerically pure form using a reductive cyclization strategy. N-Boc α-amino nitriles were deprotonated and alkylated with enantiomerically pure dibromides to afford the first ring. The products were manipulated to introduce phosphate leaving groups, and subsequent reductive lithiation followed by intramolecular alkylation formed the second ring with high stereoselectivity. The third ring was formed by intramolecular displacement of a mesylate by the deprotected amine. Lepadiformine A and B contain a hydroxymethyl group adjacent to the amine. This appendage was introduced in a sequence using a Polonovski-Potier reaction as the key step. The synthetic strategy is stereoselective and convergent and demonstrates the utility of N-Boc α-amino nitriles as linchpins for alkaloid synthesis.

Synthesis of tetrahydroisoquinoline alkaloids via anodic cyanation as the key step

We report a new route to tetrahydroisoquinoline (THIQ) alkaloids involving the alkylation of alpha-aminonitrile 2 as a key step. The latter compound was prepared by anodic cyanation of the corresponding tertiary amine 1. Reductive decyanation of alpha-aminonitriles 6a-c proceeded diastereoselectively (up to 95% de) to deliver the C1-substituted alkaloids precursors 9a-c. The syntheses of (+/-)-carnegine, (+/-)-norlaudanosine, and (+/-)-O,O-dimethylcoclaurine have been achieved.

A unified approach to polyene macrolides: synthesis of candidin and nystatin polyols

Polyene macrolide antibiotics are naturally occurring antifungal agents. Members of this class include amphotericin B, which has been used widely to treat systemic fungal infections. A general synthetic strategy has been devised to prepare polyol chains associated with the polyene macrolides. Cyanohydrin acetonide alkylations were used to assemble the carbon skeleton, and a simple modification of the strategy allowed an advanced intermediate to be converted to either the candidin polyol or the nystatin polyol. The candidin polyol was further elaborated to a protected candidin aglycone. This strategy will be applicable to other members of the polyene macrolide natural products.