Stephen P. Waters

Enantioselective Formal Total Synthesis of (+)-Aspergillide C

An enantioselective formal total synthesis of the cytotoxic macrolide (+)-aspergillide C has been accomplished from (S)-(-)-glyceraldehyde acetonide and the Danishefsky-Kitahara diene. Strategic transformations include a hetero Diels-Alder reaction, Ferrier-type addition, and palladium-catalyzed oxidative lactonization to set key stereocenters within the dihydropyran core, followed by fragment coupling via (E)-selective Julia-Kocienski olefination.

Room-Temperature Aromatization of Tetrahydro-β-carbolines by 2-Iodoxybenzoic Acid: Utility in a Total Synthesis of Eudistomin U

2-Iodoxybenzoic acid is a convenient reagent for the dehydrogenation of tetrahydro-β-carbolines to their aromatic forms under mild conditions. The utility of the method was demonstrated in a total synthesis of the marine indole alkaloid eudistomin U.

Synthesis of the isocoumarin portion of the rubromycins

Abstract A synthesis of the isocoumarin found in the rubromycin class of natural products is reported. The isocoumarin ring system is formed via Heck coupling of a pyruvate synthon with a terephthalic acid derivative followed by an intramolecular acid-catalyzed cyclization. The requisite terephthalic acid precursor is generated by carboxylation of catechol and then desymmetrization of the aromatic ring by halogenation. The isocoumarin derivative that has been produced is an appropriate precursor for the synthesis of γ-rubromycin, purpuromycin, and heliquinomycin.

Concise total syntheses of the Lycopodium alkaloids (+/-)-nankakurines A and B via luciduline.

Total syntheses of the Lycopodium alkaloids nankakurines A and B have been accomplished in 6 and 7 steps, respectively, via a sequence that passes through a third Lycopodium alkaloid, luciduline, and forgoes the use of protecting groups on nitrogen. Key features include a short preparation of luciduline followed by a concise and stereoselective aminoallylation/ring-closing metathesis protocol to fashion the spiropiperidine ring common to nankakurines A and B.

An aza-Prins cyclization approach to functionalized indolizidines from 2-allylpyrrolidines.

The stereoselective synthesis of a diverse set of functionalized indolizidine systems has been accomplished through the aza-Prins cyclization of 2-allylpyrrolidines. The condensation of aldehydes onto 2-allylpyrrolidines yields iminium ions that undergo highly diastereoselective aza-Prins cyclization, producing up to two stereogenic centers and two new rings in one step.

Pyridone Annulation via Tandem Curtius Rearrangement/6π-Electrocyclization: Total Synthesis of (−)-Lyconadin C

A concise, enantioselective total synthesis of the Lycopodium alkaloid (-)-lyconadin C was achieved in 12 steps and high overall yield. Key features include construction of a luciduline congener through Mannich-type cyclization and a one-pot, tandem Curtius rearrangement/6π-electrocyclization to fashion the 2-pyridone system of lyconadin C.

Development of a 2-Aza-Cope-[3+2] Dipolar Cycloaddition Strategy for the Synthesis of Quaternary Proline Scaffolds

A one-pot multicomponent procedure for the synthesis of highly functionalized pyrrolidine rings through a domino 2-aza-Cope-[3 + 2] dipolar cycloaddition sequence has been demonstrated. This protocol was found to be both high-yielding and stereoselective for the endo cycloadduct.

Synthesis of functionalized indolizidines through Pauson-Khand cycloaddition of 2-allylpyrrolidines.

A concise entry to functionalized indolizidine scaffolds through a domino 2-aza-Cope-[3 + 2] dipolar cycloaddition and Pauson-Khand [2 + 2 + 1] cyclization has been accomplished. The process was conducted under mild conditions to afford diverse indolizidine systems as single diastereomers in good overall yields.

A new entry to azomethine ylides from allylic amines and glyoxals: shifting the reliance on amino ester precursors.

The first examples of azomethine ylides derived from allylic amine and glyoxal precursors are reported. The condensation of primary allylic and α-aryl amines with glyoxylates or α-aryl glyoxals affords conjugated azomethine ylides that undergo facile [3 + 2] cycloaddition, providing 5-alkenyl pyrrolidine cycloadducts that cannot be accessed through the classical use of amino esters as ylide precursors.