Total Synthesis of Manzamine A and Related Alkaloids

Total syntheses of three structurally complex marine natural products, manzamine A, ircinol A, and ircinal A, are reported. The route pivoted on the construction of a late-stage protecting-group-free pentacyclic enol triflate coupling partner, from which all three family members were accessed divergently via palladium-catalyzed reactions. The rapid synthesis of this key pentacyclic enol triflate was achieved by a highly convergent union of five fragments through a stereoselective Michael addition, a three-component nitro-Mannich lactamization cascade, an unprecedented and highly stereoselective reductive nitro-Mannich cyclization cascade, a stereoselective organometallic addition, and a <i>Z</i>-selective alkene ring-closing metathesis. Altogether this chemistry has allowed the shortest synthetic route to date for manzamine A (18-step longest linear sequence) via a late-stage diversification point that is ideal for future manzamine A analogue synthesis

Total Synthesis of Manzamine A and Related Alkaloids

Total syntheses of three structurally complex marine natural products, manzamine A, ircinol A, and ircinal A, are reported. The route pivoted on the construction of a late-stage protecting-group-free pentacyclic enol triflate coupling partner, from which all three family members were accessed divergently via palladium-catalyzed reactions. The rapid synthesis of this key pentacyclic enol triflate was achieved by a highly convergent union of five fragments through a stereoselective Michael addition, a three-component nitro-Mannich lactamization cascade, an unprecedented and highly stereoselective reductive nitro-Mannich cyclization cascade, a stereoselective organometallic addition, and a <i>Z</i>-selective alkene ring-closing metathesis. Altogether this chemistry has allowed the shortest synthetic route to date for manzamine A (18-step longest linear sequence) via a late-stage diversification point that is ideal for future manzamine A analogue synthesis

Gold and BINOL-Phosphoric Acid Catalyzed Enantioselective Hydroamination/<i>N</i>‑Sulfonyliminium Cyclization Cascade

A highly enantioselective hydroamination/<i>N</i>-sulfonyliminium cyclization cascade is reported using a combination of gold(I) and chiral phosphoric acid catalysts. An initial 5-<i>exo</i>-dig hydroamination and a subsequent phosphoric acid catalyzed cyclization process provide access to complex sulfonamide scaffolds in excellent yield and high enantiocontrol. The method can be extended to lactam derivatives, with excellent yields and enantiomeric excesses of up to 93% ee

Synthetic Chameleon Turns into Oximes, Nitrones, and Hydroxylamines when Exposed to Blue Light

A metal-free, user-friendly photochemical transformation of nitroalkanes to oximes, nitrones, and hydroxylamines has been developed. The visible-light-induced reactions are catalyzed by the readily available photoredox organocatalyst 4CzIPN and use inexpensive amines as reductants. Broad in scope and tolerant of multiple functional groups and heterocycles, the transformation proceeds under mild conditions. Its synthetic potential was demonstrated in the formal total synthesis of amathaspiramide F. A basic insight into the reaction mechanism was gained with the help of an NMR study

Synthetic Chameleon Turns into Oximes, Nitrones, and Hydroxylamines when Exposed to Blue Light

A metal-free, user-friendly photochemical transformation of nitroalkanes to oximes, nitrones, and hydroxylamines has been developed. The visible-light-induced reactions are catalyzed by the readily available photoredox organocatalyst 4CzIPN and use inexpensive amines as reductants. Broad in scope and tolerant of multiple functional groups and heterocycles, the transformation proceeds under mild conditions. Its synthetic potential was demonstrated in the formal total synthesis of amathaspiramide F. A basic insight into the reaction mechanism was gained with the help of an NMR study

Total Synthesis of (−)-Himalensine A

The first enantioselective synthesis of (−)-himalensine A has been achieved in 22 steps. The synthesis was enabled by a novel catalytic, enantioselective prototropic shift/furan Diels–Alder (IMDAF) cascade to construct the ACD tricyclic core. A reductive radical cyclization cascade was utilized to build the B ring, and end-game manipulations featuring a molecular oxygen mediated γ-CH oxidation, a Stetter cyclization to access the pendant cyclopentenone, and a highly chemoselective lactam reduction delivered the natural product target

Total Synthesis of (−)-Himalensine A

The first enantioselective synthesis of (−)-himalensine A has been achieved in 22 steps. The synthesis was enabled by a novel catalytic, enantioselective prototropic shift/furan Diels–Alder (IMDAF) cascade to construct the ACD tricyclic core. A reductive radical cyclization cascade was utilized to build the B ring, and end-game manipulations featuring a molecular oxygen mediated γ-CH oxidation, a Stetter cyclization to access the pendant cyclopentenone, and a highly chemoselective lactam reduction delivered the natural product target

Total Synthesis of (−)-Himalensine A

The first enantioselective synthesis of (−)-himalensine A has been achieved in 22 steps. The synthesis was enabled by a novel catalytic, enantioselective prototropic shift/furan Diels–Alder (IMDAF) cascade to construct the ACD tricyclic core. A reductive radical cyclization cascade was utilized to build the B ring, and end-game manipulations featuring a molecular oxygen mediated γ-CH oxidation, a Stetter cyclization to access the pendant cyclopentenone, and a highly chemoselective lactam reduction delivered the natural product target