Synthesis and odour evaluation of novel sulfur‐containing cyclic acetals

Some sulfur‐containing compounds are known as useful flavours, but they have the drawback of instability in flavour composition. Therefore, we decided to develop stable sulfur‐containing compounds. We focused on 3‐mercapto‐2‐butanone (1), which is known for a meat‐like flavour. The carbonyl group of 1 was acetalized to improve the stability and to develop new flavouring compounds. We expected the resulting steric hindrance to also improve the stability of mercapto group. We synthesized 11 novel acetals based on these hypotheses. As a result, we were successful in the development of stable sulfur‐containing cyclic acetals with attractive odours. We developed eleven novel sulfur‐containing cyclic acetals as flavoring compounds by acetalizing α‐mercaptoketone such as 3‐mercapto‐2‐butanone. Cyclic acetal moiety of the synthetic compounds deactivated the mercapto group due to steric hindrance to increase stability of sulfur‐containing compounds. The odor also changed by acetalization.