(R)-(+)-[VCD(–)984]-4-Ethyl-4-methyloctane: A Cryptochiral Hydrocarbon with a Quaternary Chiral Center. (1) Synthesis of the Enantiopure Compound and Unambiguous Determination of Absolute Configuration

✍ Scribed by Takuma Fujita; Kazuhiro Obata; Shunsuke Kuwahara; Atsufumi Nakahashi; Kenji Monde; John Decatur; Nobuyuki Harada

• Publisher: John Wiley and Sons
• Year: 2010
• Tongue: English
• Weight: 696 KB
• Volume: 2010
• Category: Article
• ISSN: 1434-193X
• DOI: 10.1002/ejoc.201000777

✦ Synopsis

Abstract

Enantiopure (R)‐(+)‐[VCD(–)984]‐4‐ethyl‐4‐methyloctane (1), a cryptochiral hydrocarbon with a quaternary chiral center, was synthesized by the use of 2‐methoxy‐2‐(1‐naphthyl)propionate (MαNP) and (–)‐camphorsultam dichlorophthalic (CSDP) acid methods. The diastereomeric MαNP and CSDP acid esters prepared from racemic 2‐butyl‐2‐methyl‐1‐tetralols, were effectively separated by HPLC on silica gel, and their absolute configurations were unambiguously determined by X‐ray crystallographic analysis and ^1^H NMR anisotropy methods. The recovered enantiopure 2‐butyl‐2‐methyl‐1‐tetralol [(1__S__,2__S__)‐(+)‐cis‐9] was then converted into the hydrocarbon (+)‐1, the R absolute configuration of which was unambiguously determined for the first time. The structure of hydrocarbon 1 was also confirmed by NMR HSQC‐TOCSY analysis.