Montecrinanes A-C: Triterpenes with an Unprecedented Rearranged Tetracyclic Skeleton from Celastrus vulcanicola. Insights into Triterpenoid Biosynthesis Based on DFT Calculations.
Three new triterpenoids with an unprecedented 6/6/6/6-fused tetracyclic carbon skeleton, montecrinanes A-C (1-3), were isolated from the root bark of Celastrus vulcanicola, along with known D:B-friedobaccharanes (4-6), and lupane-type triterpenes (7-12). The stereostructures of the new metabolites were elucidated based on spectroscopic (1D and 2D NMR) and spectrometric (HR-EIMS and HR-ESIMS) techniques. Their absolute configurations were determined by both NMR spectroscopy, with (R)-(-)-α-methoxyphenylacetic acid as a chiral derivatizing agent, and biogenetic considerations. Biogenetic pathways for montecrinane and D:B-friedobaccharane skeletons were proposed and studied by DFT methods. The theoretical results support the energetic feasibility of the putative biogenetic pathways, in which the 1,2-methyl shift from the secondary baccharenyl cation represents a novel and key reaction step for a new montecrinane skeleton.
Instituto Universitario de Bio-Orgánica "Antonio González", and Departamento de Química, Universidad de La Laguna, C/Astrofísico Francisco Sánchez 2, 38206, La Laguna, Tenerife, Spain.
Martín
http://orcid.org/0000-0001-5288-5216
M
Purino
Instituto Universitario de Bio-Orgánica "Antonio González", and Departamento de Química, Universidad de La Laguna, C/Astrofísico Francisco Sánchez 2, 38206, La Laguna, Tenerife, Spain.|Departamento de Química, Facultad de Ciencias, Universidad de Chile, Las Palmeras, 3425, Ñuñoa, Santiago, Chile.
Alejandro E
http://orcid.org/0000-0002-7188-6342
AE
Ardiles
Instituto Universitario de Bio-Orgánica "Antonio González", and Departamento de Química, Universidad de La Laguna, C/Astrofísico Francisco Sánchez 2, 38206, La Laguna, Tenerife, Spain.
Oliver
http://orcid.org/0000-0002-3395-9213
O
Callies
Instituto Universitario de Bio-Orgánica "Antonio González", and Departamento de Química, Universidad de La Laguna, C/Astrofísico Francisco Sánchez 2, 38206, La Laguna, Tenerife, Spain.
Ignacio A
http://orcid.org/0000-0002-0641-607X
IA
Jiménez
Instituto Universitario de Bio-Orgánica "Antonio González", and Departamento de Química, Universidad de La Laguna, C/Astrofísico Francisco Sánchez 2, 38206, La Laguna, Tenerife, Spain. ilopez@ull.es.
Isabel L
http://orcid.org/0000-0002-7698-2704
IL
Bazzocchi
D031247:Celastrus / Q000737:chemistry*; D004544:El Salvador; D008962:Models, Theoretical; D015394:Molecular Structure; D019906:Nuclear Magnetic Resonance, Biomolecular; D024301:Plant Bark / Q000737:chemistry; D014315:Triterpenes / Q000737:chemistry / Q000302:isolation & purification* / Q000378:metabolism
D014315:Triterpenes; C000621467:montecrinane A; C000621468:montecrinane B; C000621469:montecrinane C
biosynthesis; density functional calculations; natural products; structure elucidation; terpenoids