Synthesis of ω-Methylsulfinyl- and ω-Methylsulfonylalkyl Glucosinolates

TL;DR

This paper describes new methods to synthesize specific types of plant compounds called glucosinolates, which are important for their potential health benefits.

Contribution

The paper introduces two general synthetic pathways for ω-methylsulfinyl- and ω-methylsulfonylalkyl glucosinolates.

Findings

Selective S-oxidation of ω-methylsulfanyl analogs produced sulfoxide or sulfone counterparts in moderate yields.

A nitronate chlorination strategy enabled the preparation of key intermediates for coupling with glucopyranose.

The methods yielded target compounds like glucoraphanin for future bioactivity studies.

Abstract

General pathways were devised to synthesize ω-methylsulfinyl- and ω-methylsulfonylalkyl glucosinolates, which represent an important class of structurally homogeneous plant specialized metabolites. The first approach was based on the selective S-oxidation of ω-methylsulfanyl analogs previously obtained in our laboratory, producing the corresponding sulfoxide or sulfone counterparts in moderate yields. In an alternative approach, previously prepared ω-nitroalkyl methylsulfide precursors were selectively oxidized either to sulfoxides or to sulfones. The key-thiofunctionalized hydroximoyl chloride intermediates were prepared in situ from sulfoxides or sulfones using a nitronate chlorination strategy. A coupling reaction with 1-thio-β-d-glucopyranose was directly applied, followed by O-sulfation of the intermediate thiohydroximates. The final deprotection of the sugar moiety produced the target compounds, including renowned glucoraphanin and homologs, intended for further bioactivity investigations.

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