delta(13)C- and delta(18)O-values of glycerol of food fats.

The average values of carbon and oxygen isotopic contents (delta(13)C and delta(18)O) of 36 glycerol samples from fats have been determined. The examined samples arise from many fats of animal and plant origin, as well as from the three Italian hard cheeses Parmigiano-Reggiano, Grana Padano and Trentingrana. The total (13)C content allows one to distinguish between glycerol from plants with the C-4 carbon fixation pathway (maize, mean delta(13)C = -14.4 per thousand) and that from plants with the C-3 pathway (mean delta(13)C = -30.7 per thousand). The delta(13)C-values of glycerols of animal origin seem to depend on the diet of the animal, as suggested by the mean values -29.6, -29.0 and -25.1 per thousand, respectively, observed for Parmigiano-Reggiano, Trentingrana and Grana Padano. Additionally, the mean total (18)O content of glycerol samples of vegetable origin is approximately 23.8 per thousand, while that from animal fat is 15.1 per thousand. However, the delta(18)O mean values relative to Parmigiano-Reggiano, Grana Padano and Trentingrana are 11.8, 16.0 and 13.8 per thousand, respectively. The combination of the (13)C and (18)O measurements relative to the fat glycerol of the three cheeses might be considered a potential criterion of authentication.

Stable isotope characterization of raspberry ketone extracted from Taxus baccata and obtained by oxidation of the accompanying alcohol (Betuligenol).

The natural abundance (2)H NMR characterization of raspberry ketone 1 extracted from himalayan Taxus baccata and of the accompanying (R) carbinol 2 is performed and compared with that of samples of 1 obtained from 2 by oxidation with Candida boidinii and CrO(3), respectively. The determination of the delta((13)C) and/or delta((18)O) values of the above extractive products and of benzoic acid (6) and 4-butylphenol (10), obtained from natural of synthetic 1, and of 4-phenylbutan-2-ol (8), prepared from extractive 2, allows a description of the labeling pattern of this set of products. A graph of (D/H)(3)/(D/H)(2) vs (D/H)(5)/(D/H)(4) (Figure 3) of the presently examined samples and of those previously characterized in the laboratory, including three commercial samples sold as natural, defines three areas, containing (a) the material of botanical origin and that produced from extractive 2 by biooxidation, (b) those produced by bioreduction of the unsaturated ketone 3, and (c) the synthetic samples.

Enantiomer separation of alpha-ionone using gas chromatography with cyclodextrin derivatives as chiral stationary phases.

The gas chromatographic enantiomer separation of alpha-ionone was studied with three different chiral stationary phases using as chiral selectors: (1) heptakis(2,3,6-tri-O-methyl)-beta-cyclodextrin, dissolved in polysiloxane PS-086, (2) octakis(2,6-di-O-pentyl-3-O-trifluoroacetyl)-gamma-cyclodextrin and (3) octakis(2,6-di-O-pentyl-3-O-butanoyl)-gamma-cyclodextrin, both dissolved in polysiloxane SE-54. The influence of the concentration of the chiral selector in the polysiloxane, coated on Chromosorb P AW-DMCS 80-100 mesh, is described and discussed, as well as the effect of Chromosorb loading. The feasibility of the preparative gas chromatographic separation of the enantiomers of alpha-ionone is considered; in order to provide a term of comparison, the estimated performances are compared with those achieved in the separation of the enantiomers of the inhalation anaesthetic enflurane.

Natural Abundance (2)H Nuclear Magnetic Resonance Study of the Origin of Raspberry Ketone.

The site-specific natural abundance deuterium distribution of raspberry ketone 3 obtained through a variety of methods has been determined through (2)H NMR spectroscopy. This technique provided a means of distinguishing between "natural" raspberry ketones biogenerated from 4-hydroxybenzalacetone (2), obtained from 4-hydroxybenzaldehyde of extractive botanical origin and acetone produced by sugar fermentation by reduction using baker's yeast and other microorganisms, and other raspberry ketone samples obtained in different "non-natural" ways. Of natural origin is also a commercial sample obtained in an unspecified manner. A mechanistic interpretation has been proposed to explain the difference of site-specific deuterium content between the examined samples.

Determination of the (13)C Content of Glycerol Samples of Different Origin.

The average carbon isotope value (delta(13)C) of 63 samples of glycerol from over 30 different sources has been determined. The results indicate that it is possible to distinguish the glycerol obtained from the glycerides produced in plants following C-3 and C-4 carbon fixation pathways. The samples obtained from animal sources seem to reflect the composition of the material consumed, as well as that produced by sugar fermentation.

A nuclear magnetic resonance method for the determination of the purity of commercial dequalinium chloride.

4-amino-1-(10-4'-quinaldinylaminodecyl)quinaldinium chloride (3) has been identified through nuclear magnetic resonance (NMR) studies as one of the impurities of a commercial sample of dequalinium chloride (CAS 522-51-0). The NMR technique is proposed as a rapid method for the recognition and quantification of the impurities in dequalinium chloride samples.

Kinetic resolution of substituted 1,3-4H-5,6-dihydrooxazines with carboxylesterase NP: synthesis of (3S,1'R)-3-(1'-hydroxyethyl)-azetidin-2-one.

The kinetic resolution of oxazinyl-ethyl carboxylates 4, is reported employing carboxylesterase NP as biocatalyst. Starting from the anti racemic stereoisomers 4c-d, the unreacted ester is obtained in 40% yield and 93% e.e. The enantiomeric acid is obtained in the open form. Cyclization of the latter and base equilibration allows recycling of the undesired stereoisomer. Compound 4d has the absolute configuration required in the azetidinone 3d, an intermediate in the synthesis of penems and carbapenems.

Stereochemistry and synthetic applications of products of fermentation of alpha,beta-unsaturated aromatic aldehydes by baker's yeast.

Baker's yeast fermenting on D-glucose converts 2-substituted C6-C3 alpha,beta-unsaturated aromatic aldehydes into the corresponding 3-phenylprop-2-en-1-ols and 3-phenylpropan-1-ols, and into the 4-substituted (2S,3R)-5-phenylpent-4-en-2,3-ols. The formation of the C6-C3 alcohols from the aldehydes by baker's yeast was already known, but the production of the methyl diols is new. The conversion of C6-C3 alpha,beta-unsaturated aldehydes into the C6-C5 methyl diols can be viewed as the overall consequence of two distinct chemical operations: (1) addition of a C2 unit equivalent to acetaldehyde onto the Si-face of the carbonyl carbon of the unsaturated aldehyde forms the (R)-alpha-hydroxy ketone in an acyloin-type condensation, and (2) reduction of this intermediate on the Re-face of the carbonyl gives the diol actually isolated. There is some tolerance by the enzymic system(s) involved in the reaction(s) leading from the C6-C3 alpha,beta-unsaturated aromatic aldehydes to the 4-substituted (2S,3R)-5-phenylpent-4-en-2,3-ols as far as the structure of the aromatic aldehydes and the substitutents in the alpha position are concerned, but acetaldehyde is the only aldehyde accepted as second terminus of the reaction. However, synthetic alpha-hydroxy ketones, prepared from aldehydes that cannot be directly converted by yeast into the corresponding methyl diols, are reduced by yeast. This indicates that the reason direct conversion of the aldehydes does not occur is that these materials probably cannot be accepted as substrates by the condensing enzyme(s). The (2S,3R)-diols can be used instead of natural carbohydrates as starting materials for the synthesis of optically active forms of natural products belonging to different structural classes. Applications of these diols in the synthesis of L-daunosamine, the natural form of vitamin E and other products are discussed.

On the synthesis of serine and homoserine samples asymmetrically labelled with tritium and deuterium in the hydroxymethylene group.

(1R) [1-3H, 2H1] 3-Phenylpropanol, the key intermediate in the synthesis of (4R) [4-3H, 2H1] D,L-homoserine and of the (4S)-isomer, is obtained from (1S) [1-2H1] 3-phenylpropanol and (1RS) [1-3H] ethanol upon incubation with yeast alcohol dehydrogenase and NAD+; under similar conditions 2-phenylethanol undergoes very small exchange with [1-2H2] ethanol.