Structure-odour correlation, Part XXIII. 2-alkyl-3a-methyltetrahydro-4-oxa-1,3-dithia- and -3,4-dioxa-1-thia-pentalenes

The 2-alkyl-3a-methyl-tetrahydro-4-oxa-1,3-dithiapentalenes la-f were prepared from the chloropentanone 4, the α-bromo thioacetates 9a-f and H2S/NEt3 via the labile intermediates 6a-f. Likewise, the 3,4-dioxa-1-thia analogues 2a-f were obtained from 4 and the α-bromoacetates 10a-f via 11a-f. The stereochemistry of the ring fusion and the syn- or anti-position of the 2-alkyl group were assigned by NOED spectra. Flavour evaluation showed that 1b and c possess similar onion-like, meaty, metallic and sulphury notes as described for the parent compound 1a. The taste of 2a-f in general exhibits meaty, sulphury, thiamine-like and fatty tonalities.