An asymmetric Claisen rearrangement using Oppolzer’s camphorsultam was developed. Under thermal conditions, a geraniol-derived substrate underwent the rearrangement with good stereoselectivity. The absolute configuration of the newly formed all-carbon quaternary stereocenter was confirmed by the total synthesis of (+)-bakuchiol from the rearrangement product.

https://www.mdpi.com/1420-3049/17/11/13330/pdf

Asymmetric Construction of All-Carbon Quaternary Stereocenters by Chiral-Auxiliary-Mediated Claisen Rearrangement and Total Synthesis of (+)-Bakuchiol

A practical stereoselective synthesis of (S)-bakuchiol (1) and its enantiomer is reported. The important intermediate, (R)-configured β-siloxy aldehyde 5, was obtained in three steps from the easily available material geraniol (2) via the key step of Yamamoto's rearrangement of epoxy silyl ethers. (S)-Bakuchiol (1) and its enantiomer, (R)-bakuchiol (17), were finally obtained in different synthetic sequences with overall yields of 51% (ten steps) and 40% (nine steps) from geraniol (2), respectively.

Stereoselective Total Synthesis of Natural (S)-Bakuchiol and Its Enantiomer

A short synthesis of (±)-bakuchiol was achieved starting with geranylindium sesquibromide and 2-(4-methoxyphenyl)acetaldehyde.

Short synthesis of (±)-bakuchiol via a geranylindium reagent

Lewis acid-induced reaction of γ-substituted allylstannanes with aldehydes proceeded at the α-, β- or γ-position, depending upon the nature of the substituents.

Diversity in the Lewis acid-induced reaction of aldehydes with γ-substituted allylstannanes depending upon the substituent

PRACTICAL PREPARATION OF RESVERATROL 3-O-β-D-GLUCURONIDE

The synthesis of the racemate of the naturally occurring phenol, bakuchiol, p-(3,7-dimethyl-3-vinylocta-trans-1,6-diimyl)phenol, is reported. The key step was the in situ formation and Claisen rearrangement of the geranyl enol ether of acetophenone to 1-p-methoxyphenyl-3,7-dimethyl-3-vinyloct-6-en-1-one (IIIa). Bakuchiol cyclised readily in the presence of acid.

J. Carnduff

Papers

The synthesis of (±)-bakuchiol

The synthesis of (±)-bakuchiol