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Absolute configuration of phomactatriene diterpenoids obtained by Wagner‐Meerwein rearrangement of epimeric verticillols
Author(s) -
RíoChávez Ángel A.,
GarcíaGutiérrez Hugo A.,
RománMarín Luisa U.,
BeizaGranados Lidia,
CerdaGarcíaRojas Carlos M.,
JosephNathan Pedro,
HernándezHernández Juan D.
Publication year - 2019
Publication title -
chirality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.43
H-Index - 77
eISSN - 1520-636X
pISSN - 0899-0042
DOI - 10.1002/chir.23061
Subject(s) - chemistry , conformational isomerism , absolute configuration , stereochemistry , vibrational circular dichroism , density functional theory , computational chemistry , circular dichroism , molecule , organic chemistry
The epimeric diterpenes (+)‐(1 S ,3 E ,7 E ,11 S ,12 S )‐verticilla‐3,7‐dien‐12‐ol ( 1 ), isolated from Bursera suntui , and (+)‐(1 S ,3 E ,7 E ,11 S ,12 R )‐verticilla‐3,7‐dien‐12‐ol ( 2 ), isolated from Bursera kerberi , gave the same Wagner‐Meerwein rearrangement product (−)‐(1 E ,4 Z ,8 Z ,11 S ,12 R )‐phomacta‐1,(15)4,8‐triene ( 3 ). The Et 2 O:BF 3 ‐induced transformations evidence that verticillenes and phomactanes, both containing the bicyclo[9.3.1]pentadecane skeleton, are biogenetically related through the verticillen‐12‐yl cation ( A + ), which also is a key intermediate in the biosynthetic pathways to generate antitumor taxanes. Molecular modeling using the Monte Carlo protocol, followed by density functional theory (DFT) geometry optimization employing the hybrid functionals B3LYP and B3PW91, both with the DGDZVP basis set, secured the configuration of 3 as followed from the good agreement between the calculated and experimental vibrational circular dichroism spectra. Similar DFT calculations allowed determining the absolute configuration of (+)‐(1 R ,4 R ,5 R ,8 S ,9 S ,11 S ,12 R ,15 R )‐1,15:4,5:8,9‐triepoxyphomactane ( 9 ), which surprisingly derives from epoxidation of the second minimum energy conformer of 3 .