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. 2018 Oct 31:14:2737-2744.
doi: 10.3762/bjoc.14.252. eCollection 2018.

Synthesis of a tyrosinase inhibitor by consecutive ethenolysis and cross-metathesis of crude cashew nutshell liquid

Jacqueline Pollini  1 , Valentina Bragoni  1 , Lukas J Gooßen  1
Affiliations

Synthesis of a tyrosinase inhibitor by consecutive ethenolysis and cross-metathesis of crude cashew nutshell liquid

Jacqueline Pollini et al. Beilstein J Org Chem. .

Abstract

A convenient and sustainable three-step synthesis of the tyrosinase inhibitor 2-hydroxy-6-tridecylbenzoic acid was developed that starts directly from the anacardic acid component of natural cashew nutshell liquid (CNSL). Natural CNSL contains 60-70% of anacardic acid as a mixture of several double bond isomers. The anacardic acid component was converted into a uniform starting material by ethenolysis of the entire mixture and subsequent selective precipitation of 6-(ω-nonenyl)salicylic acid from cold pentane. The olefinic side chain of this intermediate was elongated by its cross-metathesis with 1-hexene using a first generation Hoveyda-Grubbs catalyst, which was reused as precatalyst in a subsequent hydrogenation step. Overall, the target compound was obtained in an overall yield of 61% based on the unsaturated anacardic acid content and 34% based on the crude CNSL.

Keywords: cashew nutshell liquid; cross-metathesis; renewable feedstock; sustainable chemistry; tyrosinase inhibitor.

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Figures

Scheme 1
Scheme 1
Targeted conversion of CNSL into a tyrosinase inhibitor.
Scheme 2
Scheme 2
Previous synthesis of 2-hydroxy-6-tridecylbenzoic acid by Fu et al.
Scheme 3
Scheme 3
Ethenolysis of the crude CNSL.
Figure 1
Figure 1
State-of-the-art metathesis catalysts.
Scheme 4
Scheme 4
Overall process in a preparative scale.
See this image and copyright information in PMC

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