Due to their intrinsic physical properties, which includes being able to perform as volatile liquids at room and biological temperatures, fragrance ingredients/intermediates make ideal candidates for ...continuous-flow manufacturing. This review highlights the potential crossover between a multibillion dollar industry and the flourishing sub-field of flow chemistry evolving within the discipline of organic synthesis. This is illustrated through selected examples of industrially important transformations specific to the fragrances and flavours industry and by highlighting the advantages of conducting these transformations by using a flow approach. This review is designed to be a compendium of techniques and apparatus already published in the chemical and engineering literature which would constitute a known solution or inspiration for commonly encountered procedures in the manufacture of fragrance and flavour chemicals.
The enzymatic reduction of carboxylic acids is in its infancy with only a handful of biocatalysts available to this end. We have increased the spectrum of carboxylate‐reducing enzymes (CARs) with the ...sequence of a fungal CAR from Neurospora crassa OR74A (NcCAR). NcCAR was efficiently expressed in E. coli using an autoinduction protocol at low temperature. It was purified and characterized in vitro, revealing a broad substrate acceptance, a pH optimum at pH 5.5–6.0, a Tm of 45 °C and inhibition by the co‐product pyrophosphate which can be alleviated by the addition of pyrophosphatase. The synthetic utility of NcCAR was demonstrated in a whole‐cell biotransformation using the Escherichia coli K‐12 MG1655 RARE strain in order to suppress overreduction to undesired alcohol. The fragrance compound piperonal was prepared from piperonylic acid (30 mM) on gram scale in 92 % isolated yield in >98% purity. This corresponds to a productivity of 1.5 g/L/h.
An improved synthesis of enantiomerically pure(S, E)-(+)-5-methylhept-2-en-4-one from(S)-(+)-2-methyl-1-butanol in four steps is reported.
An improved chiral-pool synthesis of enantiomerically ...pure(S)-(+)-filbertone, starting from(S)-(+)-2-methyl-1-butanol in four steps is reported.
Display omitted
A number of bicyclic macrolides with two stereogenic centres formally derived from ω-cycloalkyl fatty acids were synthesised by ring enlargement of cycloalkanones with novel chiral building blocks, ...easily available from yeast reduction products of β-keto esters. A comparison with structurally related monocyclic macrolides revealed surprising effects of structural variations on the olfactory properties.
The odour of chiral bicyclic macrolides like 1a was investigated. The indicated bond disconnections lead to flexible monocyclic analogues with surprising effects on the olfactory properties.
(9
Z)-Dodec-9-en-12-olide (
1), also known as “Yuzu lactone”, a volatile ingredient of Yuzu fruit was prepared in a three step synthesis via
Z-selective Wittig olefination, a deprotection and ...activation protocol and subsequent cyclization by solid-liquid phase transfer catalysis under avoidance of high dilution conditions.
The synthesis of the title compound
1 and its organoleptic properties are reported.
Both enantiomers of 13-pentadecanolide and 15-heptadecanolide, higher analogues of galbanum macrolides, were prepared via ring enlargement of cyclodecanone and cyclododecanone, respectively. ...Conversion of the intermediate oxo lactones to methylenated ethyl galbanum macrolides by Wittig olefination shifted the olfactory properties dramatically.
Both enantiomers of the higher analogues of galbanum macrolides 3a and 3b were synthesised. This structural change shifted the olfactory properties dramatically and stimulated further modifications.
PDF
