Fragrant Aldehydes Research Articles

Novel fragrant aldehydes from (1R,5R)-sabinene: An experimental study supported by DFT calculations revealing an unusual hydroformylation mechanism

The fragrance industry continually searches for compounds that introduce new scent notes or improve existing ones. Herein, we report a methodology for obtaining two novel aldehydes, potentially interesting for application in fragrance formulations, via rhodium-catalyzed hydroformylation of (1R,5R)-sabinene, a biorenewable monoterpene available in many essential oils. One of the aldehydes, which retained the original sabinene skeleton, was derived from the hydroformylation of the exocyclic C-C double bond through the accepted hydroformylation mechanism. The other aldehyde arose from the interaction of rhodium with the cyclopropane ring through an unusual mechanism, which resulted in the cyclopropane ring cleavage, forming a product that shares structural similarities with established fragrant molecules. The selectivity was controlled by adjusting the reaction conditions (temperature, pressure, P-ligand, and P/Rh ratio). Each aldehyde was obtained in a 70–80 % yield, depending on the reaction conditions. Combining our experimental findings with DFT calculations allowed us to propose an unusual hydroformylation reaction mechanism involving cyclopropane moiety in vinylcyclopropanes.

Basidiomycota strains as whole-cell biocatalysts for the synthesis of high-value natural benzaldehydes

Substituted benzaldehydes are the most commonly used natural-occurring flavours in the world. The consumer’s preference for ‘natural or organic’ aromas has increased the request for flavours possessing the ‘natural’ status. The resulting shortage of aromatic aldehydes of extractive origin, such as vanillin, veratraldehyde and piperonal, can be offset by developing a new biotechnological synthesis method. Here, we report a study on the microbiological reduction of five natural benzoic acid derivatives, namely p-anisic, vanillic, veratric, piperonylic and eudesmic acids, to produce the corresponding fragrant aldehydes. We found that different Basidiomycota strains can efficiently perform this transformation, with good chemical selectivity and tolerance to the toxicity of substrates and products. Besides confirming the carboxylic acid reductase activity of the already studied fungi Pycnoporus cinnabarinus, we discovered that other species such as Pleurotus eryngii, Pleurotus sapidus and Laetiporus sulphureus as well as the non-ligninolytic fungi Lepista nuda are valuable microorganisms for the synthesis of anisaldehyde, vanillin, veratraldehyde, piperonal and 3,4,5-trimethoxybenzaldehyde from the corresponding acids. According to our findings, we propose a reliable process for the preparation of the above-mentioned aldehydes, in natural form.Key points• Fragrant benzaldehydes were obtained by biotransformation.• Basidiomycota strains reduced substituted benzoic acid to the corresponding aldehydes.• Anisaldehyde, vanillin, veratraldehyde, piperonal and 3,4,5-trimethoxybenzaldehyde were prepared in natural form.Graphical

Substituent effect on controlled release of fragrant aldehydes from pH-triggered nicotinoylhydrazone-based precursors

The acidic hydrolysis of nicotinoylhydrazone-based fragrance precursors reveals that a strong electron-donating substituent speeds up the release rate, whereas a weak electron-donating group has the opposite result in buffered solutions and on cotton.

Microwave-assisted synthesis and odor characteristics of some new isoxazolidines

We describe herein the design and synthesis of new isoxazolidin-5-carboxylates by microwave-assisted 1,3-dipolar cycloadditions of aldonitrones, derived from five fragrant aldehydes, with methacrylate esters. The reaction proceeded regioselectively providing mostly endo- diastereomers and in some cases an inseparable mixture of endo-exo products. The structures of target compounds were identified on the basis of IR, NMR, and TOF-MS measurements. Besides, both aldonitrone and isoxazolidine derivatives were subjected to olfactory evaluation by an expert nose. Diverse fragrance notes were observed in each series of isoxazolidines bearing different groups from aldonitrones. However, their odor ranges were found as animalic, medical, waxy, and ozonic undertones in common.

Phytochemical Characterization of Extracts from Fagraea Fragrans and Juglans Regia by GC-MS Analysis

Fagraea fragrans and Juglans regia have several therapeutic applications. The present study aimed to analyze the phytochemical compositions of a methanolic crude extract from the stem bark of F. fragrans and an oily liquid from a chloroform extract of seeds of J. regia. Approximately, 220 g of methanolic crude extract (yield = ca. 5%) was obtained from the stem bark of F. fragrans from hot-solvent extraction, and approximately, 45 g of chloroform oily liquid (yield = ca. 1.5%) was obtained from the seeds of J. regia by maceration technique. The phytochemical compositions of these two extracts were analyzed separately by injecting an aliquot of 1.0 μL solution of each extract prepared in hexane to a GC-MS instrument fitted with a DB-5 column of the dimension 50 m × 0.25 mm, i.d., 0.25 μm film thickness. The presence of fourteen components, including fragrant aldehydes and bioactive sterols, was identified in the methanolic crude extract and the presence of eight components, including fatty acids, fatty esters, and γ-tocopherol, was identified in the chloroform oily liquid. For the first time, we report the presence of γ-tocopherol (3.46%), n-hexanoic acid (1.26%), ethyl hexadecanoate (4.70%), ethyl oleate (6.59%), and a high content of ethyl linoleate (29.93%) in this chloroform oily liquid. From this study, we concluded that F. fragrans and J. regia have bioactive compounds of pharmaceutical importance. Therefore, these compounds can be extracted from these plants for therapeutic applications.

Identification of Copper-Containing Oxidoreductases in the Secretomes of Three Colletotrichum Species with a Focus on Copper Radical Oxidases for the Biocatalytic Production of Fatty Aldehydes.

Copper radical alcohol oxidases (CRO-AlcOx), which have been recently discovered among fungal phytopathogens, are attractive for the production of fragrant fatty aldehydes. With the initial objective to investigate the secretion of CRO-AlcOx by natural fungal strains, we undertook time course analyses of the secretomes of three Colletotrichum species (C. graminicola, C. tabacum, and C. destructivum) using proteomics. The addition of a copper-manganese-ethanol mixture in the absence of any plant-biomass mimicking compounds to Colletotrichum cultures unexpectedly induced the secretion of up to 400 proteins, 29 to 52% of which were carbohydrate-active enzymes (CAZymes), including a wide diversity of copper-containing oxidoreductases from the auxiliary activities (AA) class (AA1, AA3, AA5, AA7, AA9, AA11, AA12, AA13, and AA16). Under these specific conditions, while a CRO-glyoxal oxidase from the AA5_1 subfamily was among the most abundantly secreted proteins, the targeted AA5_2 CRO-AlcOx were secreted at lower levels, suggesting heterologous expression as a more promising strategy for CRO-AlcOx production and utilization. C. tabacum and C. destructivum CRO-AlcOx were thus expressed in Pichia pastoris, and their preference toward both aromatic and aliphatic primary alcohols was assessed. The CRO-AlcOx from C. destructivum was further investigated in applied settings, revealing a full conversion of C6 and C8 alcohols into their corresponding fragrant aldehydes. IMPORTANCE In the context of the industrial shift toward greener processes, the biocatalytic production of aldehydes is of utmost interest owing to their importance for their use as flavor and fragrance ingredients. Copper radical alcohol oxidases (CRO-AlcOx) have the potential to become platform enzymes for the oxidation of alcohols to aldehydes. However, the secretion of CRO-AlcOx by natural fungal strains has never been explored, while the use of crude fungal secretomes is an appealing approach for industrial applications to alleviate various costs pertaining to biocatalyst production. While investigating this primary objective, the secretomics studies revealed unexpected results showing that under the oxidative stress conditions we probed, Colletotrichum species can secrete a broad diversity of copper-containing enzymes (laccases, sugar oxidoreductases, and lytic polysaccharide monooxygenases [LPMOs]) usually assigned to "plant cell wall degradation," despite the absence of any plant-biomass mimicking compound. However, in these conditions, only small amounts of CRO-AlcOx were secreted, pointing out recombinant expression as the most promising path for their biocatalytic application.

Minor constituents of essential oils and aromatic extracts. Oximes derived from natural flavor and fragrance raw materials – Sensory evaluation, spectral and gas chromatographic characteristics

A small library of 57 low molecular weight oximes was prepared from fragrant aldehydes and ketones, and their olfactory profiles were determined. The most substantive and interesting in terms of the sensory impressions were (+)-isomenthone oxime (fresh, musty, green) and cyclocitral oxime (earthy with patchouli, moss and leather notes). The linear retention indices (LRI) were determined for DB-1, DB-5 and DB-WAX columns, and E/Z isomers of 22 out of 57 compounds were resolved on the DB-5 column. Attempts were made to resolve enantiomers of the chosen oximes on chiral GC columns. The best results were obtained by using a Cyclosil B column, on which the enantiomers of camphor, menthone, piperitone and carvone oximes were fully resolved. NMR and MS spectra were acquired to characterize the synthesized library. Gas chromatography–olfactometry was used to assess odoriferous properties of both isomers of oximes. In most cases both isomers possessed similar profile and intensity.

Matrix effect on the degradation of fragrant aldehydes: oxidation versus chlorination in an antiperspirant formulation

ABSTRACTThe oxidative degradation of several fragrant aldehydes in an antiperspirant base has been investigated. The different products formed have been detected and identified by GC‐MS. It is shown that, besides the oxidation products, i.e. mainly the corresponding acid resulting from the Baeyer–Villiger reaction, several unexpected chlorinated products are formed through interactions with aluminium chlorhydrate and the suspension agent. The supposed intermediate in the chlorination pathway is the acyl hypochlorite R(CO)OCl which can react according to either an ionic or a radical route. Reactive species involved in these mechanisms are Clδ+ and Cl•, respectively. The common intermediate for the autoxidation and oxychlorination processes is the peracid R(CO)OOH. Copyright © 2013 John Wiley & Sons, Ltd.

Oxidative degradation of fragrant aldehydes. Autoxidation by molecular oxygen

The oxidative degradation of fragrant aldehydes by molecular oxygen has been investigated. The oxygen consumption was monitored and the bond dissociation energy (BDE) of the aldehyde C(O)–H bond were calculated by DFT method. The oxidation products were identified by GC/MS. The different pathways accounting for the oxidative degradation are discussed. The main product is the acid, beside the formate ester. Both oxidation products result from the Baeyer–Villiger reaction involving a peracid R(CO)OOH whereas minor products arise from the hydroperoxide ROOH intermediate derived either from the acyl peroxy radical, R(CO)OO or from the decarboxylation of the peracid RC(O)OOH.

Preparation of Imidazolidin‐4‐ones and Their Evaluation as Hydrolytically Cleavable Precursors for the Slow Release of Bioactive Volatile Carbonyl Derivatives

AbstractImidazolidin‐4‐ones are suitable in practical applications as hydrolytically cleavable precursors for the controlled release of fragrant aldehydes and ketones. The corresponding profragrances were prepared by treating aliphatic carbonyl compounds with commercially available amino acid amines in the presence of a base to yield mixtures of diastereomers. The two diastereomers isolated from the reaction of glycinamide hydrochloride with (–)‐menthone were separated by column chromatography. The absolute stereochemistry of the isomers was determined by NMR spectroscopy and confirmed by X‐ray single crystal structure analysis. Under acidic conditions and in protic solvents, the two diastereomers slowly isomerized without releasing the ketone. The hydrolysis of the precursors was investigated by solvent extraction from buffered aqueous solutions and a cationic surfactant emulsion, as well as by dynamic headspace analysis after deposition onto a cotton surface. Generally, ketones were shown to be more readily released than aldehydes. Increasing the size of the substituents at C‐5 decreased the rate of hydrolysis in solution and on the cotton surface. Glycinamide‐based imidazolidin‐4‐ones were more efficient than the corresponding oxazolidin‐4‐ones or oxazolidines. Neither the release rates in solution, nor the hydrophobicity of the precursor structure (which influences deposition), nor the combination of these two parameters allowed easily predicting the performance of the delivery systems in application.

Fragrant chitosan nanospheres: Controlled release systems with physical and chemical barriers

Existing fragrance controlled release systems are either based on a physical barrier, such as entrapment of the fragrant molecules inside the micro- or nano-spheres, or a chemical barrier, such as labile chemical bonds. Here, we propose a system with a combination of the two approaches but fabricated via a simple surfactant free one step process using biodegradable chitosan polymer. The fabrication process involves a chemical reaction to covalently link the fragrant aldehydes with the amine functionalities of the N-succinylchitosan (NS-chitosan) carriers that simultaneously leads to an ultrasonic aided reorganization of the spheres in such a way that the grafted entities are at the particles’ core. Localization of the grafted imine moieties at the core of the imine-NS-chitosan particles was confirmed by X-ray photoelectron spectroscopy (XPS) analysis. The obtained fragrant chitosan nanospheres not only showed up to 85-fold fragrance prolongation but also dispersed well in water.

Applied Photochemistry – Light Controlled Perfume Release

Ambient light is one of the most suitable available trigger conditions for the release of covalently bound volatile odorants in home- and laundry-care applications. We report on three complementary classes of light-cleavable fragrance precursors, covering the controlled release of odorants with a wide range of functional groups. o-Hydroxy cinnamates 1 undergo a UV-induced double bond isomerization followed by transesterification to release coumarin and a fragrance alcohol of choice. ?-Alkoxyacetophenones 10 and ?,?-dialkoxyacetophenones 12 undergo Norrish type II fragmentations upon UV-irradiation, thereby releasing one or two equivalents of fragrant aldehydes, respectively. Finally, photoexcited Xanthenoic esters 22 undergo fragmentation to release reactive acyl radicals, which further cyclize onto internal olefins to form perfumery lactones of various ring sizes.

Prenuptial perfume: Alloanointing in the social rituals of the crested auklet (Aethia cristatella) and the transfer of arthropod deterrents

Alloanointing, the transfer of chemicals between conspecifics, is known among mammals, but hitherto, the behavior has not been documented for birds. The crested auklet (Aethia cristatella), a colonial seabird of Alaskan and Siberian waters, alloanoints during courtship with fragrant aldehydes that are released from specialized wick-like feathers located in the interscapular region. Crested auklets solicit anointment at the colony, and prospective mates rub bill, breast, head, and neck over wick feathers of their partners. This distributes aldehydes over the head, neck, and face where the birds cannot self-preen. The resulting chemical concentrations are sufficient to deter ectoparasites. Auklets that emit more odorant can transfer more defensive chemicals to mates and are thus more sexually attractive. Behavioral studies showed that crested auklets are attracted to their scent. Wild birds searched for dispensers that emitted their scent and rubbed their bills on the dispensers and engaged in vigorous anointment behaviors. In captive experiments, naïve crested auklets responded more strongly to synthetic auklet scent than controls, and the greatest behavioral response occurred during early courtship. This study extends scientific knowledge regarding functions of alloanointing. Alloanointing had previously been attributed to scent marking and individual recognition in vertebrates. Alloanointing is described here in the context of an adaptive social cue--the transfer of arthropod deterrents between prospective mates.

Chemical Modification and some Aligned Composites of Chitosan in a Filament State

AbstractThe mono‐filaments (> 10 m in length) of chitosan and the blends of chitosan‐collagen, chitin‐collagen and chitin‐silk fibroin were wet‐spun. The mono‐filaments were chemically N‐modified with each of n‐fatty acid anhydrides, intra‐molecular carboxylic anhydrides, fragrant aldehydes and transition metal ions. The mono‐filament was aligned on a straight line with the mono‐filament of silk fibroin or poly(ethylene terephthalate) (PET), and a bundle of one to three mono‐filaments was coated with a medium of sericin (Se), chitosan or N‐acylchitosan to give rise to novel silk‐mimic filament composites. The filaments coated with a medium of sericin exhibited 26–27 denier for the titer, 2.46–3.36 gf · denier−1 for the tenacity and 11.8–25.0% for the elongation. The apparent density (denier · μm−1 in the filament diameter) of the filament composites was about 3–4 times higher than that of the mono‐filaments. Portion of fragrant aldehydes in Schiff's base was slowly hydrolyzed at room temperature by contacting with atmospheric moisture in the open air, and released from the fragrant filaments and composites. The filament composites coated with a chitosan medium were thrombogenic, and those coated with N‐acylchitosans were antithrombogenic.An illustrated model for a silk‐mimic filament composite, N0(N2I‐FI).magnified imageAn illustrated model for a silk‐mimic filament composite, N0(N2I‐FI).

Some fragrant fibres and yarns based on chitosan

Novel fragrant chitosan derivatives, fibres and yarns were prepared. The degree of substitution (d.s.) for Schiff's base was at 0.25–1.00 in the solution state and at 0.19–0.89 in the fibre state. The fragrant chitosan fibres had 4.50–5.16 denier for the titer, 0.40–1.05 gf/denier for the tenacity and 3.9–14.5% for the elongation. A bundle of two silk fibroin filaments was coated with a layer of chitosan, and the chitosan layer was N-modified with the fragrant aldehydes to give rise to fragrant yarns. The yarns had 24.0–33.2 denier for the titer, 2.02–2.75 gf/denier for the tenacity and 9.6–16.9% for the elongation. A portion of the fragrant aldehydes was slowly released from the fragrant chitosan derivatives, fibres and yarns in the open air at room temperature, but little released in a closed dry glass vessel.

The essential oil of pectis papposa

This oil, produced by a heavily scented herbaceous plant of the American Southwest and northern Mexico, is rich in cumaldehyde and carvone, and is therefore a potential commercial source of these fragrant aldehydes, now obtained from cumin, caraway and dill seed oils and used in Savoring food and beverages.