Lactones, detection

Other lactones detected include a-butyrolactone and pantolactone (2,4-hydroxy-3,3-dimethylbutyrolactone), both of which are typical of sherries. Besides the duration of aging, their concentration is closely linked to yeast strain (Zea et al., 1995). Another lactone, solerone (4-... 

Other lactones detected include a-butyrolactone and pantonolactone (2,4-dihyd-roxy-3,3-dimethylbutyrolactone), which is deemed typical of sherry wines. Both have been associated with specific yeast races (Zea et al. 1995) and the aging time (Cortes 2002). 

B Arnicae flos (A, montana, A. chamissonis 5a-8a). The CHCt, extracts of Arnicae flos ( method see Sect. 7.1.1), developed in system PE, contain sesquiterpene lactones, detectable as violet-grey zones witlt ZM reagent (vis). 

The reaction of 5-methoxy-2(5//)-furanone 168 with amines was also studied (89T6799). The conjugated addition of ethanolamine to the furanone 168 gave the racemic amino lactone 275 (R = CH2CH20H). Similarly, piperazine reacted with two equivalents of 168 to provide the diadduct 276 as a single diastereomer (no traces of the other isomer were detected). With tryptamine, the reaction was nearly quantitative with the the formation the tran -adduct 277 (R = tryptophanyl) (Scheme 72) (89T6799). 

Schaefer, A. L., Hanzelka, B. L., Parsek, M. R., and Greenberg, E. P. (2000). Detection, purification, and structural elucidation of the acylhomoser-ine lactone inducer of Vibrio fischeri luminescence and other related molecules. Method. Enzymol. 305 288-301. 

When it does occur, the Bal2 mechanism is easy to detect, since it is the only one of the base-catalyzed mechanisms that requires inversion at R. However, in the last example given, the mechanism is evident from the nature of the product, since the ether could have been formed in no other way. The Aal2 mechanism has been reported in the acid cleavage of y-lactones. ° ... 

High concentrations of endosulfan sulfate were found primarily in the liver, intestine, and visceral fat 24 hours after mice were exposed to a single dose of -endosulfan (Deema et al. 1966). Five days following a single oral administration of " C-endosulfan to rats, the diol, sulfate, lactone, and ether metabolites were detected in the feces (Borough et al. 1978). In sheep, endosulfan sulfate was detected in the feces, and endosulfan alcohol and a-hydroxyether were detected in the urine (Gorbach et al. 1968). 

Endosulfan and metabolites were observed in the urine of workers who had prepared and applied endosulfan for 2-5 hours either 1 day or 1 week prior to sampling, without using protective clothing or face mask (thus, exposure was probably both dermal and inhalation) (Vidal et al. 1998). Unchanged a-and P-endosulfan and endosulfan ether were the predominant chemicals excreted 1 day following exposure. One week after exposure, a-endosulfan was detected in urine of four of five workers, but P-endosulfan was detected in only one of five samples and endosulfan ether was not detected at all. Endosulfan sulfate was detected in only one of five samples at 1 week after exposure and in none of the four samples at 1 day postexposure. Endosulfan lactone was detected in one of four and one of five samples at 1 day and 1 week after exposure, respectively. 

An enzyme immunoassay technique has been employed for measuring endosulfan and its degradation products (i.e., endosulfan diol, endosulfan sulfate, endosulfan ether, and endosulfan lactone) in water at 3 ppb (Chau and Terry 1972 Musial et al. 1976). However, this technique is not currently in use in environmental residue analysis. Further research into this technique could produce a rapid, rehable, and sensitive method for identifying contaminated areas posing a risk to human health. No additional methods for detecting endosulfan in environmental media appear to be necessary at this time. However, methods for the determination of endosulfan degradation products are needed. 

Chromatography. A number of HPLC and TLC methods have been developed for separation and isolation of the brevetoxins. HPLC methods use both C18 reversed-phase and normal-phase silica gel columns (8, 14, 15). Gradient or iso-cratic elutions are employed and detection usually relies upon ultraviolet (UV) absorption in the 208-215-nm range. Both brevetoxin backbone structures possess a UV absorption maximum at 208 nm, corresponding to the enal moeity (16,17). In addition, the PbTx-1 backbone has an absorption shoulder at 215 nm corresponding to the 7-lactone structure. While UV detection is generally sufficient for isolation and purification, it is not sensitive (>1 ppm) enough to detect trace levels of toxins or metabolites. Excellent separations are achieved by silica gel TLC (14, 15, 18-20). Sensitivity (>1 ppm) remains a problem, but flexibility and ease of use continue to make TLC a popular technique. 

When the natural product source contains racemic mixtures (of isomeric forms), then clearly the assignment of signal value to either or both variants of a compound needs to be determined. Alterations in receptor detection of chirality can change sensitivity to the geometrically alternate compound over the range 101 to 106. Of the lactones passed into urine and deposited on tarsal hairs of Black-tailed deer (Odocoileus... 

Initiators such as (306) initiate the ROP of CL to form telechelic triblock diols.478 Molecular weights approach theoretical values with polydispersities <1.3 and no significant level of transesterification was detected at up to 95% conversions. Alternative bimetallic samarium initiators have been used to synthesize aromatic, cumulene and amine/imine link-functionalized poly(lactones).479... 

The ionization potentials, using mass spectrometry, for both 2-hydroxy-and 3-hydroxythiophenes have been compared with data for compounds derived from either tautomeric form in order to analyze the tautomeric composition.124 125 In the 2-hydroxy-substituted system the enol isomer could not be detected. Of the two possible unsaturated lactones the oc,/l-unsaturated form was the major isomer. In the 3-hydroxy-substituted case both the oxo form and the enol form are important. The position of the equilibrium was compared with those of the corresponding furan and sele-nophene systems for both isomers. 

The 1,3-dipolar cycloadditions of nitrones (551), (595), (614), (615) and their enantiomers (595 ent), (614 ent), (615 ent) (Fig. 2.40) to a.p-unsaturated y-lactones, such as achiral D7 g and D-glycero D7 h, provide an interesting example of double asymmetric inductions. The reactions are kinetically controlled. However, on heating and at longer reaction times, the reversibility of the cycloaddition (595 + D7 h) was observed, and the presence of a more stable thermodynamic product (620) was detected. Moreover, in the case of lactone D7 h, a... 

Like in gangliosides, lactones might be found in some bacterial capsular polysaccharides containing 1-carboxyethylsubstituents. But their identification remains problematic due to the conditions of isolation and preparation of analytic samples. To facilitate their detection by NMR, and in order to determine if the formation or hydrolysis of lactones occurred during analytical procedures, synthetic model substances, 2,3- and/or 3,4-lactones based on gluco-12, manno-13, and galactopyranosides 14 were prepared and characterized by NMR spectroscopy (Fig. 2).20 The relative lactonisation rates in acetic acid-fi 4 and hydrolysis rates in buffered D20 were evaluated. 

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