The chemical synthesis of aliphatic benzo[b][1,4]dioxepin-3-one analogues related to synthetic marine odorants

Odour discrimination is a combinatorial phenomenon, as odorant molecules are known to bind to multiple olfactory receptors. It is also considered that the absolute configuration of a molecule is of crucial importance in determining the human perception of odour. Additionally, it is also recognised that a substance evokes a sense of smell provided that its molecular shape is compatible with the complementary space within the olfactory receptor.<br><br>Since the benzo[b][1,4]dioxepin-3-one scaffold represents the essential structural characteristics of the synthetic marine odorant family, we were therefore interested in the effect of modulating the molecular shape via an aromatic/aliphatic ring exchange. By the substitution of the aromatic functionality with a saturated ring counterpart we endeavoured to discover the molecular interactions of the carbocyclic ring systems with olfactory receptor sites, including any potential chiral interactions occurring within the receptor(s).<br><br>Our initial results revealed that an aromatic ring system was necessary for binding to the marine odorant receptor(s) and that the addition of an alkene or methyl substituent had little effect on receptor affinity. The synthesised aliphatic benzo[b][1,4]dioxepin-3-one analogues instead exhibited a plethora of odorant descriptors and consequently it was speculated that perhaps altogether new odorant families could be targeted by further chemical synthesis. It was also questioned if the fusion of 1,4-dioxepan-6-one heterocyclic rings onto naturally occurring terpenoid odorants could merge/synergise existing fragrance classes. The chemical synthesis and olfactory characterisation of a variety of aliphatic benzo[b][1,4]dioxepin-3-one analogues, as well as a series of 2-substituted and 2,3-annulated 1,4-dioxepan-6-one analogues is hereby reported.