Synthesis 2023; 55(08): 1198-1206
DOI: 10.1055/a-1984-9689
paper

Chemoenzymatic Enantioselective Synthesis of the Hancock Alkaloids (S)- and (R)-Galipeine, (S)-Cuspareine, (S)-Galipinine, and (S)-Angustureine

Nilton Gonçalves da Cruz
a   Department of Chemistry, Federal University of Minas Gerais, Belo Horizonte, MG, 31270-901, Brazil
,
Amanda Silva de Miranda
a   Department of Chemistry, Federal University of Minas Gerais, Belo Horizonte, MG, 31270-901, Brazil
,
Henriete da Silva Vieira
a   Department of Chemistry, Federal University of Minas Gerais, Belo Horizonte, MG, 31270-901, Brazil
,
Markus Kohlhoff
b   Chemistry of Bioactive Natural Products, René Rachou Institute, Oswaldo Cruz Foundation (FIOCRUZ), Belo Horizonte, MG, 30190-002, Brazil
,
João Guilherme Pereira Mendonça
c   Department of Biochemistry and Molecular Biology, Federal University of Viçosa, Viçosa, MG, 36570-900, Brazil
,
Marisa Alves Nogueira Diaz
c   Department of Biochemistry and Molecular Biology, Federal University of Viçosa, Viçosa, MG, 36570-900, Brazil
,
a   Department of Chemistry, Federal University of Minas Gerais, Belo Horizonte, MG, 31270-901, Brazil
› Author Affiliations
We are grateful to the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (Brazilian Federal Agency for Support and Evaluation of Graduate Education, CAPES) for granting a master’s scholarship to N.G.C. We are also grateful for the financial support provided by the Fundação de Amparo à Pesquisa do Estado de Minas Gerais (Minas Gerais Research Foundation, FAPEMIG).


Abstract

The enantioselective synthesis of the Hancock 1,2,3,4-tetrahydroquinoline alkaloids (S)-galipeine, (S)-cuspareine, (S)-galipinine, and (S)-angustureine and the nonnatural enantiomer (R)-galipeine is described herein. The target compounds were obtained in five steps from a racemic quinaldinic acid derived α-amino ester in overall yields of 21.2% to 37.5%. The synthetic route comprised two key steps: an enzymatic kinetic resolution to control the C-2 stereocenter, affording (R)- and (S)-α-amino esters as key chiral intermediates with 94% and 72% ee, respectively, and Wittig olefination of (R)- and (S)-α-amino aldehyde synthons with the corresponding phosphonium salts using a phase-transfer system (t-BuOH/CH2Cl2), thereby allowing the introduction of alkyl substituents at C-2. Finally, the enantioselective synthesis was concluded with the catalytic hydrogenation of olefinic bonds on the Wittig adducts to furnish the target Hancock alkaloids, including (R)-galipeine, whose synthesis is described here for the first time.

Supporting Information



Publication History

Received: 08 October 2022

Accepted: 23 November 2022

Accepted Manuscript online:
23 November 2022

Article published online:
03 January 2023

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