Navegando por Palavras-chave "Absolute configuration"

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    7.1′,8.3′- and 7.3′,8.5′-Connected Bicyclo[3.2.1]octanoids and Oxabicyclo[3.2.2]nonane-Type Neolignans from Ocotea aciphylla: Structures and Absolute Configurations
    (ACS, 2024-02-23) Santos, Carlos Henrique Totini dos; Petrica, Edith Eunice Arthut; Batista, Andrea Nastri de Luca; Rodrigues, Edilene Delphino; Garcez, Walmir Silva; Albuquerque, Ana Carolina Ferreira de; Santos Jr, Fernando Martins dos; Batista Jr, Joao Marcos [UNIFESP]; Garcez, Fernanda Rodrigues; http://lattes.cnpq.br/4209224090500050
    The phytochemical investigation of the leaves and trunk bark of a specimen of Ocotea aciphylla collected in the southern portion of the Amazon forest led to the isolation of an oxabicyclo[3.2.2]nonane-type neolignan and 15 bicyclo[3.2.1]- octanoid neolignans, 14 of which are unreported compounds (2− 15), including one with an unusual oxidation pattern of the side chain at C-1′ and two rare 7.1′,8.3′-connected bicyclo[3.2.1]- octanoid derivatives. Their structures and relative configurations were determined by extensive spectrometric analysis based on 1D- and 2D-NMR spectroscopy and HRESIMS data, while their absolute configurations were unambiguously assigned using electronic and vibrational circular dichroism data assisted by density functional theory calculations. Additionally, known sesquiterpenes, phenylpropanoids, and phytosterols were also isolated
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    Stereochemistry of natural products from vibrational circular dichroism
    (RSC, 2025-08-23) Batista, Andrea Nastri de Luca; Valverde, Alessandra Leda; Nafie, Laurence A.; Batista Junior, Joao Marcos [UNIFESP]; http://lattes.cnpq.br/4209224090500050
    Secondary metabolites from land and marine (micro)organisms have been at the focus of the drug discovery process for many years. One of the reasons for this success is nature’s incredible ability to create intricate molecular scaffolds. Such structural richness, however, makes the structural elucidation, and the absolute configuration assignment in particular, a challenging process. Vibrational circular dichroism (VCD) has emerged as one of the most reliable and versatile methods to unambiguously assign both the absolute configuration and conformations of chiral molecules in solution. Although VCD is no longer a curiosity in the field of molecular spectroscopy after 50 years since its first report, it is still underutilized by natural product chemists worldwide for varying reasons. Herein, we highlight the evolution of the application of VCD to natural product chemistry, focusing on its strengths as well as points that still need improvement. General guidelines for the correct application of VCD to stereochemical studies are also provided.