Synthesis and NMR Spectroscopic Elucidation of Four Diastereoisomers of Oxygenated Bisabolane Side Chain. Issue 8 (August 2015)

• Record Type: Journal Article
• Authors: Hirai, Misaki; Miyazaki, Rurina; Mitsui, Kana; Kiuchi, Kota; Onuki, Hiroyuki; Hirota, Hiroshi; Kuroda, Chiaki
• Is Part Of: Helvetica chimica acta. Volume 98:Issue 8(2015:Aug.)
• Page Start: 1035
• Page End: 1060
• Publication Date: 2015-08
• Subjects: Chemistry -- Periodicals; Chemistry, Analytical -- periodicals; Chimie -- Périodiques; 540
• DOI: 10.1002/hlca.201400395
• Languages: English
• ISSNs: 0018-019X

Abstract

<abstract abstract-type="main" xml:lang="en"> <title>Abstract</title> <p>Four possible stereoisomers of a model compound of highly O‐bearing bisabolane sesquiterpenes were synthesized and their NMR spectra were compared. Starting from isopulegol, allylic oxidation and <italic>Grignard</italic> reaction afforded a mixture of alcohols at C(8), which was separated. After metathesis reaction, both <italic>α</italic>‐ and <italic>β</italic>‐epoxides were obtained <italic>via</italic> non‐stereoselective epoxidation, while VO(OⁱPr)₃‐catalyzed epoxidation afforded a single diastereoisomer selectively. NMR Spectra of twelve synthesized compounds, four stereoisomers of acetates, isobutyrates, and tiglates, were measured. A difference between C(8<italic>α</italic>)‐ and C(8<italic>β</italic>)‐acyloxy isomers was observed in the <italic>δ</italic>‐values of HC(8) in CDCl₃. Within the 8<italic>β</italic>‐acyloxy compounds, the <italic>α</italic>‐ and the <italic>β</italic>‐epoxides were distinguished by either the <italic>J</italic>‐value of HC(8) or the chemical shift of CH₂(9). Within the 8<italic>α</italic>‐acyloxy compounds, two epoxide isomers were distinguished by the <italic>J</italic>‐value of HC(10) in C₆D₆ or in CD₃OD.</p> </abstract>