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The synthesis of campholenic-based fragrances requires the preservation of specific structural elements to capture the desired sandalwood scent. The most critical step of their preparation is the reduction of α,β-unsaturated carbonyl precursors while preserving the campholenic unsaturation. Classical reductions, especially hydrogenations, often lack complete chemoselectivity, leading to the formation of over-reduced byproducts. In addition, the stereochemistry plays a key role in the olfactory perception of these chiral fragrances. However, none of the current industrial syntheses are stereoselective, resulting in wasteful production of non-contributory isomers. Herein, we explore the untapped potential of biocatalytic reductions using ene-reductases (ERs) and alcohol dehydrogenases (ADHs) to enhance the sustainability of four commercial sandalwood fragrances (Brahmanol®, Firsantol®, Sandalore®, and Ebanol®), focusing on the stereoselective synthesis of their most odorant isomers. A comparison of green metrics, including E-factors and EcoScale, between bio- and chemo-based reductions is presented. [ABSTRACT FROM AUTHOR]

The production of essential oils by steam distillation is invariably associated with large amounts of organic waste which is normally disposed of or returned to the fields, although it may still contain some valuable components. In particular, Cannabis sativa essential oil produced by steam distillation of the apical part of industrial hemp plants yields a soaked biomass residue that may contain high-value cannabinoids. From the perspective of sustainable exploitation of agricultural resources, a method to extract cannabidiol (CBD) from such waste was demonstrated and scaled-up, using bioethanol as a renewable bio-based solvent and without requiring chromatographic separation, with an overall yield of 10.1 mg CBD per g waste. The work paves the way to an integrated complete utilisation of industrial hemp byproducts. Furthermore, two alternative lipase-mediated chemo-enzymatic derivatisations have been designed and optimised for the conversion of the recovered CBD into cannabielsoin (CBE), an underexploited cannabinoid with attractive bioactivity. The processes are practical and efficient, with 31--47% isolated yields and green metrics comparing well with the established chemical alternatives. [ABSTRACT FROM AUTHOR]

One-pot reactions elaborated around transition metal-catalyzed isomerization of alkenes not only offer the inherent advantages of atom-, step- and redox-economy but also enable the preparation of value-added products that would be difficult to access by conventional methods. In this Review, we cover seminal and recent examples of tandem, sequential and domino processes, which incorporate the most attractive features of olefin isomerization. [ABSTRACT FROM AUTHOR]