A new synthesis of (−)-thioambrox and its 8-epimer

This new and straightforward synthesis of (−)-thioambrox , a sulphur compound whose odour resembles ambergris, starts from sclareolide . The stereoselectivity of the final cyclization is independent of the catalyst selected, and compound is always favoured over (+)-iso-thioambrox . With hydrochloric acid as catalyst, the cyclization is unexpectedly stereospecific to give in high yield at room temperature.