Dimethyl Acetals Research Articles

Asymmetric Synthesis of Nabscessin A from Inositol and d-Camphor.

An enantiomer of nabscessin A (1), an aminocyclitol amide with antimicrobial activity, was synthesized from myo-inositol and dimethyl d-camphor acetal in 14 steps. Formal synthesis of natural nabscessin A was also achieved through the new approach to access both enantiomers of 4,5-di-O-benzyl-myo-inositol, derived from the same set of starting materials. This synthesis features utilizations of the existing framework of myo-inositol and a regioselective esterification.

Co2(CO)8-Catalyzed Reactions of Acetals or Lactones with Hydrosilanes and Carbon Monoxide. A New Access to the Preparation of 1,2-Diol Derivatives through Siloxymethylation

Abstract The Co2(CO)8-catalyzed reaction of acetals with hydrosilanes and CO under mild reaction conditions (an ambient temperature under an ambient CO pressure), leading to the production of vicinal diols is reported. A siloxymethyl group can be introduced via the cleavage of one of two alkoxy groups in the acetal. The effects of the types of hydrosilanes, acetals, solvents, and reaction temperatures on the yield of siloxymethylation products were examined in detail. The reactivity for hydrosilanes is as follows; HSiMe3 > HSiEtMe2 > HSiEt2Me > HSiEt3. Hemiacetal esters are more reactive than dimethyl acetals. The polarity of the solvent used also has a significant effect on both the course of the reaction as well as the reaction rate. The site-selective siloxymethylation can be achieved in the case of cyclic acetals such as tetrahydrofuran (THF) and tetrahydropyrane (THP) derivatives, depending on the nature of the oxygen substituent attached adjacent to the oxygen atom in the ring. When 2-alkoxy THF or THP derivatives are used as substrates, the siloxymethylation takes place with cleavage of the ring C-O bond. In contrast, the reaction of 2-acetoxy THF or THP derivatives results in siloxymethylation with the cleavage of C-OAc bond. The ring-opening siloxymethylation of lactones was also examined.

Impact of a high-fat diet on the fatty acid composition of the retina

Structure and function of the retina mainly rely on its fatty acid (FA) composition. Evidence from epidemiological studies and from animal experiments indicates that FA composition of the retina is influenced by the diet. Mice under chronic high-fat diet (HFD) develop metabolic syndrome, a risk factor for diabetes that is associated with structural and functional alterations of the retina. Here, we studied the impact of chronic exposure of mice to HFD on retinal FA composition.C57BL/6 J male mice were fed either a chow diet or a HFD for 11 weeks. As expected, HFD induced weight gain, adiposity, hyperglycemia and dyslipidemia. The retinal FA composition was determined by gas chromatography coupled to flame ionization detection. No significant change in the relative abundance of total saturated FAs (SFAs), total monounsaturated FAs (MUFAs) or total polyunsaturated FAs (PUFAs) was observed. However, retinas of HFD-fed mice displayed decreased amounts of C24:0 (p = 0.0231), C16:1n-7 (p < 0.0001), C18:1n-7 (p < 0.0001), C20:3n-9 (p = 0.0425) and C20:3n-6 (p = 0.0008), and an increased amount of C20:2n-6 (p < 0.0001). In addition, the ratio of linoleic acid (C18:2n-6) to alpha-linolenic acid (C18:3n-3) was increased in the retinas of HFD-fed mice (15.0 ± 0.8 versus 11.8 ± 0.6 in HFD and CD, respectively, p = 0.0045). No modification in the contents of arachidonic acid (C20:4n-6, AA) and docosahexaenoic acid (C22:6n-3, DHA) were observed. Analysis of dimethylacetals (DMA), which are residues of plasmalogens (Pls), revealed that the amount of Pls containing octadecanal-aldehydes (DMA C18:0) was significantly increased in HFD-fed mice (p = 0.0447). This increase was, at least in part, balanced by a decrease in Pls containing 7-octadecanal-aldehydes (DMA C18:1n-7) (p = 0.0007).In conclusion, HFD had an impact on the relative proportion of essential dietary fatty acids linoleic acid and alpha-linolenic acid that are incorporated in the retina. However, this imbalance in PUFA precursors did not alter the content of the two major retinal long-chain PUFAs, AA and DHA. HFD consumption also led to alterations in the retinal SFAs, MUFAs and Pls profiles.

The influence of habitat and sex on feral fallow deer meat lipid fraction.

The study tested the hypothesis that habitat and sex influence the composition of meat lipid fraction. Therefore, this study aims to characterize the effects of habitat and sex on feral fallow deer (Dama dama) tenderloin (psoas major muscle) intramuscular fat composition. Fallow deer meat from the Atlantic forest presented higher total cholesterol and total monounsaturated fatty acids contents, while fallow deer meat from Montado presented significantly higher proportion of total branched chain fatty acids, n-6 polyunsaturated fatty acids and dimethyl acetals. Regarding the sex influence on meat's fatty acid composition, it was observed that female fallow deer displayed higher contents of total saturated fatty acids than their male counterparts. Independently of the habitat the feral fallow deer's meat can be classified as extra lean. However, the high peroxidability index and the low total vitamin E content suggests that it is prone to lipid peroxidation. © 2020 Society of Chemical Industry.

Blautia faecicola sp. nov., isolated from faeces from a healthy human.

An obligately anaerobic, Gram-stain-positive, non-motile and coccoid- or oval-shaped bacterium, designated strain KGMB01111T, was isolated from faeces from a healthy Korean. Comparative analysis of 16S rRNA gene sequences indicated that KGMB01111T was closely related to Ruminococcus gauveauii CCRI-16110T (93.9 %) and Blautia stercoris GAM6-1T (93.7 %), followed by Clostridium nexile DSM 1787T (93.5 %), Blautia producta ATCC 27340T (93.4 %), Blautia hydrogenotrophica DSM 10507T (93.1 %) and Blautia coccoides ATCC 29236T (93.1 %) within the family Lachnospiraceae (Clostridium rRNA cluster XIVa). Phylogenetic analysis based on the 16S rRNA gene sequences indicated that KGMB01111T formed a separate branch with species in the genus Blautia. The major cellular fatty acids (>10.0 %) were C16 : 0 and C18 : 1 cis 9 dimethyl acetal (DMA), and the major polar lipids were aminophospholipids and lipids. KGMB01111T contained meso-diaminopimelic acid in cell-wall peptidoglycan. The predominant end product of fermentation produced by KGMB01111T was acetic acid. Based on the whole-genome sequence, the DNA G+C content of the isolate was 44.7 mol%. On the basis of the phenotypic, chemotaxonomic and phylogenetic characteristics, KGMB01111T represents a novel species within the genus Blautia for which the name Blautia faecicola sp. nov. is proposed. The type strain is KGMB01111T (=KCTC 15706T=DSM 107827T).

Separation and characterization of products from acidic methanolysis of plasmalogenic lipids by two-dimensional gas chromatography with online reduction

The complexity of determining the composition of animal tissue lipids is greatly increased by the presence of plasmalogens in which the alkyl chain is linked to glycerol by an enol ether bond instead of being esterified. Acidic methanolysis of animal tissue lipids provides the simultaneous scission of acyl and alkenyl ether moieties, but the complexity of the products of reaction poses a great challenge in their gas chromatographic analysis. Two-dimensional gas chromatography with online reduction (GC-OR × GC) provided the resolution of all components contained in acid methanolyzed animal lipids, taking advantage of the selective hydrogenation of alkenyl ether methanolysis products prior to the second-dimension separation (2D). In this study, we also studied the chemical transformations occurring during the acidic methanolysis of animal lipids and the subsequent gas chromatographic analysis. In particular, we observed that using methanolysis reagents contaminated with water resulted in the undesired formation of fatty aldehydes, and we made recommendations on how to avoid these side reactions using proper methanolysis conditions. Products of acidic methanolysis were studied by GC-OR × GC, GC-MS, NMR spectroscopy, and GC with flame ionization detection (GC-FID). We defined the GC-FID elution order of animal lipid acidic methanolysis products using 100 m × 0.25 mm 100% bis(cyanopropyl)siloxane columns and two different set of elution conditions: isothermal elution at 180°C, and a temperature program optimized for dairy fats. A simple procedure for isolating dimethyl acetals (DMA) prior to GC analysis is also described.

RIFM fragrance ingredient safety assessment, hydroxycitronellal dimethyl acetal, CAS Registry Number 141-92-4

Hydroxycitronellal dimethyl acetal was evaluated for genotoxicity, repeated dose toxicity, reproductive toxicity, local respiratory toxicity, phototoxicity/photoallergenicity, skin sensitization, and environmental safety. Data from read-across analog hydroxycitronellal diethyl acetal (CAS # 7779-94-4) show that hydroxycitronellal dimethyl acetal is not expected to be genotoxic. The repeated dose, reproductive, and local respiratory toxicity endpoints were evaluated using the TTC for a Cramer Class I material and the exposure to hydroxycitronellal dimethyl acetal is below the TTC (0.03 mg/kg/day, 0.03 mg/kg/day, and 1.4 mg/day, respectively). Data from hydroxycitronellal dimethyl acetal and from read-across material hydroxycitronellal diethyl acetal (CAS # 7779-94-4) show that there are no safety concerns for skin sensitization under the current declared levels of use. The phototoxicity/photoallergenicity endpoints were evaluated based on UV spectra; hydroxycitronellal dimethyl acetal is not expected to be phototoxic/photoallergenic. The environmental endpoints were evaluated; hydroxycitronellal dimethyl acetal was found not to be PBT as per the IFRA Environmental Standards, and its risk quotients, based on its current volume of use in Europe and North America (i.e., PEC/PNEC), are <1.

RIFM fragrance ingredient safety assessment, hydroxycitronellal diethyl acetal, CAS Registry Number 7779-94-4

Hydroxycitronellal dimethyl acetal was evaluated for genotoxicity, repeated dose toxicity, reproductive toxicity, local respiratory toxicity, phototoxicity/photoallergenicity, skin sensitization, and environmental safety. Data from read-across analog hydroxycitronellal diethyl acetal (CAS # 7779-94-4) show that hydroxycitronellal dimethyl acetal is not expected to be genotoxic. The repeated dose, reproductive, and local respiratory toxicity endpoints were evaluated using the TTC for a Cramer Class I material and the exposure to hydroxycitronellal dimethyl acetal is below the TTC (0.03 mg/kg/day, 0.03 mg/kg/day, and 1.4 mg/day, respectively). Data from hydroxycitronellal dimethyl acetal and from read-across material hydroxycitronellal diethyl acetal (CAS # 7779-94-4) show that there are no safety concerns for skin sensitization under the current declared levels of use. The phototoxicity/photoallergenicity endpoints were evaluated based on UV spectra; hydroxycitronellal dimethyl acetal is not expected to be phototoxic/photoallergenic. The environmental endpoints were evaluated; hydroxycitronellal dimethyl acetal was found not to be PBT as per the IFRA Environmental Standards, and its risk quotients, based on its current volume of use in Europe and North America (i.e., PEC/PNEC), are <1.

A new approach to CF3-containing 3,4-dihydroquinazolin-2(1H)-ones

A new approach to CF3-containing 3,4-dihydroquinazolin-2(1H)-ones based on the condensation of 5-acetyl-6-methyl-1-phenyl-4-trifluoromethylpyrimidin-2(1H)-one with dimethylformamide dimethyl acetal has been suggested.

Solvent-Free Synthesis of 2,5Bis((dimethylamino)methylene)cyclopentanone.

Available protocols for the synthesis of ketocyanine dyes precursor 2,5-bis((dimethylamino)methylene)cyclopentanone are not straightforward and the reported yields are low to moderate. The important feature in the synthesis of this product through organocatalyzed condensation of cyclopentanone and N,N-Dimethylformamide dimethyl acetal is the removal of methanol produced during the reaction. By studying the reaction profile, in particular the selectivity for the formation of mono- and bis-condensation products, a high yield of the desired product can be obtained through an operationally simple and solvent-free protocol.

Adj-Dicarbaporphyrinoid Systems: Synthesis, Spectroscopic Characterization, and Reactivity of 23-Carbabenziporphyrins.

A new family of adj-dicarbaporphyrinoids has been prepared using the "2 + 2" MacDonald methodology. Dibutylboron triflate catalyzed condensation of 3-iodo-4-methoxybenzaldehyde with an indene enamine afforded an iodofulvene aldehyde, and a related dimethoxyfulvene was similarly prepared in two steps from 2,4-dimethoxybenzaldehyde. Following protection as the corresponding dimethyl acetals, the iodofulvenes were metalated with Bu3MgLi at -100 °C and reacted with dimethylformamide to give the required fulvene dialdehyde intermediates. Acid-catalyzed condensation with three different dipyrrylmethanes afforded a series of benzo-23-carbabenziporphyrins in 52-70% yields. The proton nuclear magnetic resonance spectra for these adj-dicarbaporphyrinoids indicate that these macrocycles are slightly diatropic. Monoprotonation afforded cationic species with slightly larger aromatic ring currents, and under strongly acidic conditions, C-protonated dications were generated with substantial diatropic properties. The aromatic character of these structures was supported by nucleus-independent chemical shifts and anisotropy of induced current density calculations. The computational results indicate that the dications favor 23-atom 22π electron delocalization pathways. The benzo-23-carbabenziporphyrins were selectively oxidized with silver(I) acetate in dichloromethane-methanol to give stable nonaromatic structures with two additional methoxy substituents connected to sp3 hybridized bridging carbons. The intriguing reactivity and unique spectroscopic properties of benzo-23-carbabenziporphyrins make these novel structures promising candidates for further investigations.

Effects of Chestnut Tannin Extract, Vescalagin and Gallic Acid on the Dimethyl Acetals Profile and Microbial Community Composition in Rumen Liquor: An In Vitro Study.

The addition of polyphenol extracts in ruminant diets is an effective strategy to modulate rumen microflora. The aim of this in vitro trial was to study the effects of chestnut tannin extract (CHT), vescalagin (VES) and gallic acid (GAL) on dietary fibre degradability and on the dimethyl acetals (DMA) profile and microbial community composition of rumen liquor. Four diets (basal diet; basal diet plus CHT; basal diet plus VES; basal diet plus GAL) were fermented for 24 h using ewe rumen liquor. At the end of the fermentation, the microbial communities were characterized by sequencing the 16S rRNA gene. The DMA profile was analyzed by gas chromatography. Chestnut tannin extract did not affect fibre degradability, whereas VES and GAL showed a detrimental effect. The presence of CHT, VES and GAL influenced the concentration of several DMA (i.e., 12:0, 13:0, 14:0, 15:0, 18:0 and 18:1 trans-11), whereas the composition of the microbial community was marginally affected. The inclusion of CHT led to the enrichment of the genera Anaerovibrio, Bibersteinia, Escherichia/Shigella, Pseudobutyrivibrio and Streptococcus. The results of this study support the hypothesis that the activity of CHT is due to the synergistic effect of all components rather than the property of a single component.

Megasphaera lornae sp. nov., Megasphaera hutchinsoni sp. nov., and Megasphaera vaginalis sp. nov.: novel bacteria isolated from the female genital tract.

Six strictly anaerobic Gram-negative bacteria representing three novel species were isolated from the female reproductive tract. The proposed type strains for each species were designated UPII 199-6T, KA00182T and BV3C16-1T. Phylogenetic analyses based on 16S rRNA gene sequencing indicated that the bacterial isolates were members of the genus Megasphaera. UPII 199-6T and KA00182T had 16S rRNA gene sequence identities of 99.9 % with 16S rRNA clone sequences previously amplified from the human vagina designated as Megasphaera type 1 and Megasphaera type 2, members of the human vaginal microbiota associated with bacterial vaginosis, preterm birth and HIV acquisition. UPII 199-6T exhibited sequence identities ranging from 92.9 to 93.6 % with validly named Megasphaera isolates and KA00182T had 16S rRNA gene sequence identities ranging from 92.6-94.2 %. BV3C16-1T was most closely related to Megasphaera cerevisiae with a 16S rRNA gene sequence identity of 95.4 %. Cells were coccoid or diplococcoid, non-motile and did not form spores. Genital tract isolates metabolized organic acids but were asaccharolytic. The isolates also metabolized amino acids. The DNA G+C content for the genome sequences of UPII 199-6T, KA00182T and BV3C16-1T were 46.4, 38.9 and 49.8 mol%, respectively. Digital DNA-DNA hybridization and average nucleotide identity between the genital tract isolates and other validly named Megasphaera species suggest that each isolate type represents a new species. The major fatty acid methyl esters include the following: C12 : 0, C16 : 0, C16 : 0 dimethyl acetal (DMA) and summed feature 5 (C15 : 0 DMA and/or C14 : 0 3-OH) in UPII 199-6T; C16 : 0 and C16 : 1 cis 9 in KA00182T; C12 : 0; C14 : 0 3-OH; and summed feature 5 in BV3C16-1T. The isolates produced butyrate, isobutyrate, and isovalerate but there were specific differences including production of formate and propionate. Together, these data indicate that UPII 199-6T, KA00182T and BV3C16-1T represent novel species within the genus Megasphaera. We propose the following names: Megasphaera lornae sp. nov. for UPII 199-6T representing the type strain of this species (=DSM 111201T=ATCC TSD-205T), Megasphaera hutchinsoni sp. nov. for KA00182T representing the type strain of this species (=DSM 111202T=ATCC TSD-206T) and Megasphaera vaginalis sp. nov. for BV3C16-1T representing the type strain of this species (=DSM 111203T=ATCC TSD-207T).

Clostridium fungisolvens sp. nov., a new β-1,3-glucan-decomposing bacterium isolated from anoxic soil subjected to biological soil disinfestation.

Biological soil disinfestation (BSD) or reductive soil disinfestation (RSD) is a bioremediation method used to suppress or eliminate soil-borne plant pathogens by stimulating activities of indigenous anaerobic bacteria of the soil. An anaerobic bacterial strain (TW1T) was isolated from an anoxic soil sample subjected to the BSD treatment and comprehensively characterized. Cells of the strain were Gram-stain-positive, slightly curved and motile rods producing terminal spores. The strain was aerotolerant. Strain TW1T was saccharolytic and produced acetate, butyrate, H2 and CO2 as fermentation end products. Strain TW1T decomposed β-1,3-glucan (curdlan and laminarin) and degraded mycelial cells of an ascomycete Fusarium plant pathogen. Major cellular fatty acids of strain TW1T were C14 : 0, C14 : 0 dimethylacetal (DMA), C16 : 0 aldehyde and C16 : 0 DMA. Strain TW1T made a group on the phylogenetic tree constructed based on 16S rRNA gene sequences with species such as Clostridium fallax (96.3 %) and Clostridium polyendosporum (96.0 %). Whole genome analysis of strain TW1T showed that the total length of the genome was 5.28 Mb with the DNA G+C content of 31.3 mol%. The average nucleotide identity (ANIb) between strain TW1T and C. fallax was 71.2 %. Presence of the genes encoding laminarinase or GH16 β-glucosidase was confirmed from the genome analysis of strain TW1T. Based on the genomic, phylogenetic and phenotypic properties obtained, we propose strain TW1T should be assigned in the genus Clostridium in the family Clostridiaceae as Clostridium fungisolvens sp. nov. The type strain TW1T (=NBRC 112097T=DSM 110791T).

Synthesis of 2-Substituted 6-(Polyfluoromethyl)pyrimidine-4-carbaldehyde Acetals

Heterocyclization of 5,5-difluoro- and 5,5,5-trifluoro-2,4-dioxopentanal dimethyl acetals with amidines in the presence of 4 equiv of triethyl borate afforded 2-substituted 6-(difluoromethyl)- and 6-(trifluoromethyl)pyrimidine-4-carbaldehyde dimethyl acetals in high yields.

Synthesis of 2-(polyfluoromethyl)pyrimido-[1,2-a]benzimidazole-4-carbaldehyde derivatives

A simple and efficient synthesis of 2-RF-pyrimido[1,2-a]benzimidazole-4-carbaldehyde derivatives comprises the reaction between 3-(polyfluoroacetyl)pyruvaldehyde dimethyl acetals and 2-aminobenzimidazole. The effects of fluorinated substituents in 3-(polyfluoroacetyl)pyruvaldehyde dimethyl acetals and the reaction conditions on regiochemical outcome of this reaction have been estimated.

Identification and quantification of dimethyl acetals from plasmalogenic lipids in lamb intramuscular fat under different derivatization procedures

Meat lipids are mostly comprised by triacylglycerols, but small amounts of plasmalogens are also present in intramuscular fat. The purpose of this study was to evaluate the effect of lipid derivatization on the presence of dimethyl acetal (DMA) molecules from plasmalogenic lipids in intramuscular fat samples. Three different methods of methylation were assayed. Acid-catalyzed methanolysis using HCl, the traditional procedure to derivatize meat lipids, was compared to two base-catalyzed methanolysis based on the ISO International standard procedure using either KOH and/or NaOCH3 which, apparently, are only able to methylate fatty acids from triacylglycerols. DMA compounds were isolated by thin layer chromatography and then identified by gas chromatography–mass spectrometry. The most prominent DMA molecules detected were 16:0 and 18:0, but also minor amounts of monounsaturated and branched-chain DMA were quantified. Acid methylation yielded the highest amounts of DMA. However, the present article demonstrates that ISO standard based methylation procedures could also generate DMA derivatives in considerable quantities, which is not usually considered and may interfere with the determination of fatty acid methyl esters (FAME) from triacylglycerides. The current research warns scientist about possible FAME misidentifying and overestimations in intramuscular fat analysis using basic methylation and the need to consider the presence of DMA in samples that contain plasmalogens.

Brønsted acid-catalyzed facile synthesis of α-substituted N-arylaminoacetals and their downstream conversions to functionalized pyrroles

α-Substituted N-arylaminoacetals are important building blocks for organic synthesis, which can be synthesized via Mannich reaction by using glyoxal dimethyl acetal as a key precursor. As the acetal fragment was known to be susceptible to acid, in literature methods, the Mannich reaction was performed under either neutral or gently acidic conditions. As a result, only a few kinds of α-substituted N-arylaminoacetals have been synthesized via Mannich reaction until now. We found surprisingly that Mannich adducts of glyoxal dimethyl acetal, arylamines and ketones are quite stable toward strong Brønsted acid. This led us to use successfully p-toluenesulfonic acid as the acid catalyst to synthesize a broad range of α-substituted N-arylaminoacetals. The Mannich adducts could be obtained in good to excellent yields. Particularly, these products were demonstrated to be able to react with 1,3-dicarbonyl compounds in the presence of Sc(OTf)3 catalyst. A special class of multi-substituted pyrroles were thus synthesized, which can be converted to some important heterocyclic compounds including indoles and 2-formyl-N-arrylpyrroles. Dimethyl acetals of quinoline-2-carbaldehydes were also synthesized via one-pot three-component reactions of glyoxal dimethyl acetal, electron-rich anilines, and acetone.

Three-Component Cascade Reaction of 1,1-Enediamines, N,N-Dimethylformamide Dimethyl Acetal, and 1,3-Dicarbonyl Compounds: Selective Synthesis of Diverse 2-Aminopyridine Derivatives.

A novel approach has been developed for the synthesis of three kinds of highly functionalized 2-aminopyridine derivatives (APDs) through a three-component reaction of 1,1-enediamines (EDAMs) 1, N,N-dimethylformamide dimethyl acetal (DMF-DMA) 2, and 1,3-dicarbonyl compounds 3–5 via a base-promoted cascade reaction, producing the desired products in good to excellent yields. This method represents a route to obtain a novel class of APDs in a concise, rapid, and practical manner. This approach is particularly attractive because of the following features: low cost, mild temperature, atom economy, high yields, and potential biological activity of the product.

Highly Selective One-Pot Synthesis of Polysubstituted Isoflavanes using Styryl Ethers and Electron-Withdrawing ortho-Quinone Methides Generated In Situ

A highly selective one-pot synthesis of polysubstituted isoflavanes has been developed. The reaction proceeds through the cycloaddition of methyl styryl ethers, derived from phenylacetaldehyde dimethyl acetals under acidic conditions, with electron-withdrawing ortho-quinone methides generated in situ. When phenylacetaldehyde dimethyl acetals were reacted with salicylaldehydes, the reaction proceeded smoothly to afford the corresponding isoflavanes stereoselectively in high yields and with excellent regioselectivities. The present reaction provides versatile access to functionalized isoflavanes, and constitutes a useful tool for the synthesis of biologically active molecules.