Structure determination of new analogues of vardenafil and sildenafil in dietary supplements

New analogues of vardenafil and sildenafil illegally added to dietary supplements were detected by high-performance liquid chromatography (HPLC) analysis with a photodiode array detector (PDA). These compounds were isolated and their structures elucidated by mass spectrometry (MS), infrared (IR) spectroscopy, one- and two-dimensional nuclear magnetic resonance (NMR). One of the new analogues given the trivial name pseudovardenafil (compound 1) was structurally elucidated and shown to be 1-[[3-(1,4-dihydro-5-methyl-4-oxo-7-propylimidazo[5,1-f][1,2,4]triazin-2-yl)-4-ethoxyphenyl]sulfonyl]-piperidine. It was a vardenafil analogue isolated from a dietary supplement capsule. Compared with vardenafil, the piperidine ring was substituted for the ethylpiperazine group. The second new analogue, trivially named hydroxyhongdenafil (compound 2), was separated from bulk powder used as a raw material for a dietary supplement. The piperazine and phenyl groups were connected through an acetyl group instead of a sulfonyl group, and hydroxyethylpiperazine was substituted for the methylpiperazine of sildenafil. It was structurally elucidated as 5-[2-ethoxy-5-[[4-(2-hydroxyethyl)-1-piperazinyl]acetyl]phenyl]-1,4-dihydro-1-methyl-3-propyl-7H-pyrazolo[4,3-d]pyrimidin-7-one.     

帕珠沙星的合成工艺与机理

比较了以四氟苯甲酸为起始原料合成帕珠沙星的两种工艺路线,介绍了(S)-9,10-二氟-3-甲基-2,3-二氢-7-氧代-7-H-吡啶并[1,2,3-de][1,4]苯并恶嗪-6-羧酸乙酯为原料经亲核取代、脱羧水解、环丙基化、氰基水解和Hoffman重排等步骤合成帕珠沙星的反应机理,在相关机理分析的基础上对帕珠沙星的合成工艺提出了一些改进建议,并指出提高Hoffman重排反应收率、降低生产成本是帕珠沙星合成的主要研究方向.     

Basic compounds contributing to beer flavour

Sixteen basic heterocyclic compounds have been identified by g.c.-m.s. after careful extraction of a flavour essence from an English beer. They include the following that have not previously been reported as beer constituents: pyridine, 2-acetylpyridine, 3-acetylpyridine, pyrazine, methylpyrazine, 2,3-dimethylpyrazine, 2,5-dimethylpyrazine, 2,6-dimethylpyrazine, 2-ethyl-5- (and/or 6-) methylpyrazine, trimethylpyrazine, 2-ethyl-3,5-dimethylpyrazine, 2-ethyl-3,6-dimethylpyrazine, 2-ethyl-5,6-dimethylpyrazine, 6,7-dihydro-5H-cyclopentapyrazine, 2-methyl-6,7-dihydro-5H-cyclopentapyrazine, and thiazole. The minimum total concentration of basic compounds in the beer was estimated to be 10 mg/kg.     

Identification of UV photoproducts and hydrolysis products of butachlor by mass spectrometry

The photoproducts and hydrolysis products of butachlor in water were identified by gas chromatography/mass spectrometry. When exposed to UV light, butachlor in aqueous solution was rapidly degraded, giving at least 11 photoproducts as a result of dechlorination with subsequent hydroxylation or cyclization processes. The chemical structures of nine degradation compounds were identified on the basis of mass spectrum interpretation and literature data. Major photoproducts are identified as 8-ethyl-1-butoxymethyl-4-methyl-2-oxo-1,2,3,4-tetrahydro-quinoline, 2-hydroxy-2',6'-diethyl-N-(butoxymethyl) acetanilide, and a compound related to butachlor. Minor photoproducts are identified as 2,6-diethylaniline; 1-acetyl-7-ethylindole; N-(2,6-diethylphenyl)-N-(butoxymethyl)acetamide; 2-oxo-N-(2,6-diethyl-phenyl)-N-(butoxymethyl)acetamide; 1-hydroxyacetyl-2-butoxyl-3-methyl-7-ethylindole; 1-acetyl-2-butoxyl-3-methyl-7-ethylindole; and two compounds with the chemical structure unknown. The half-lives of butachlor UV photolysis were 7.54, 10.56, and 12.22 min in deionized water, river water, and paddy water, respectively. The half-lives of butachlor hydrolysis at pH 4, 7, and 10 were 630, 1155, and 1155 days at 25 +/- 1 degrees C, respectively. A hydrolysis product at pH 4 was identified by GC/MS to be 2-hydroxy-2',6'-diethyl-N-(butoxymethyl) acetanilide.     

Headspace solid-phase microextraction gas chromatography–mass spectrometry (HS-SPME-GC–MS) determination of volatile compounds in roasted plantains (French sombre and Dwarf Kalapua)

Volatile compounds from roasted plantains (French sombre, AAB) and (Dwarf Kalapua, ABB) at different stages of ripening were evaluated by a gas chromatography–mass spectrometry (GC–MS) with headspace solid-phase microextraction (HS-SPME). A total of 42 volatile compounds were identified in the roasted plantain cultivars. Some of the volatile compounds with high concentration were 2,3-dimethylpyrazine, 2-ethyl-3,5-dimethylpyrazine, (E)-2-hexenal, 2,5-dimethylpyrazine and 2,3-dihydro-5-hydroxyl-6-methyl-(4H)-pyran-4-on respectively. Principal component analysis (PCA) based on the relationships between ripening/quality of volatiles showed that 2-methyl propanol, furfural, 2,5-dimethyl pyrazine, 2,3-butanedione, guaiacol, 2-ethyl-3-methyl pyrazine, 5-, ethyl acetate, 2-pentanol, 3-isobutyl-2-methoxy pyrazine and 7,8-dihydro-β-ionol were considered to contribute significantly to the overall aroma quality of fairly riped (stages 4 & 5) and roasted plantains.     

Key odourants of pressure-cooked hen meat

The volatile aroma compounds of pressure-cooked hen meat isolated by simultaneous distillation-extraction and extraction-high vacuum distillation were investigated by GC/MS and GC-olfactometry. We found out that 2-furfuryl thiol, 3-(methylthio)propanal, 4-hydroxy-2,5-dimethyl-3(2H)-furanone, (E,E)-2, 4-decadienal, 2-methyl-3-furanthiol and 2-ethyl-3,5-dimethyl pyrazine are the most potent odourants of the pressure-cooked hen meat. We assume that aroma-active compounds such as 2,4,6-trimethyltetrahydro-1,3,5-thiadiazine, 3,5-dime-thyl-1, 2,4-trithiolane, 5,6-dihydro-2,4,6-trimethyl-4H-1,3,5-dithiazine and some unknown compounds, which could only be found in extracts obtained by simultaneous distillation-extraction, are artefacts formed during this isolation process.     

Isolation and identification of a novel sildenafil analogue adulterant in herbal products

ABSTRACT

A novel sildenafil analogue found in herbal products by a routine drug-adulteration screening programme was isolated by column chromatography. On the basis of extensive 1D- and 2D-nuclear magnetic resonance (NMR) spectroscopy and mass spectral analysis, the structure of a new compound YJ-07 was established as 1-[4-ethoxy-3-(6,7-dihydro-1-methyl-7-oxo-3-propyl-1H-pyrazolo[4,3-d]pyrimidin-5-yl) benzenesulfonamide. It common name is aminosildenafil.     

Studies on melanoidin-type colorants generated from the Maillard reaction of protein-bound lysine and furan-2-carboxaldehyde – chemical characterisation of a red coloured domaine

 The identification of a coloured substructure of melanoidin-type colorants is reported in the present paper. Brown-orange melanoidins with mass >10000 daltons were isolated from a thermally treated aqueous solution of casein and furan-2-carboxaldehyde using ultracentrifugation. After complete enzymatic digestion of the protein skeleton, two intense red coloured compounds were detected in the melanoidin hydrolysate by HPLC. These compounds were identified as the previously unknown chromophoric amino acid (S)-2-amino-6-{4-[(E)-1-formyl-2-(2-furyl)ethenyl]-5-(2-furyl)-2-[(E)-(2-furyl) methylidene]-2,3-dihydro-3-oxo-1H-pyrrol-1-yl}hexanoic acid and its 2-[(Z)-(2-furyl)methylidene] isomer, by using several NMR techniques, by MS, UV, and IR spectroscopy. The identification of these novel compounds verifies the idea that melanoidin-type colorants can be generated by a cross-linking reaction between a low molecular weight chromophore and a non-coloured high molecular weight biopolymer. Received: 19 August 1997 / Revised version: 24 October 1997     

Studies on melanoidin-type colorants generated from the Maillard reaction of protein-bound lysine and furan-2-carboxaldehyde – chemical characterisation of a red coloured domaine

 The identification of a coloured substructure of melanoidin-type colorants is reported in the present paper. Brown-orange melanoidins with mass >10000 daltons were isolated from a thermally treated aqueous solution of casein and furan-2-carboxaldehyde using ultracentrifugation. After complete enzymatic digestion of the protein skeleton, two intense red coloured compounds were detected in the melanoidin hydrolysate by HPLC. These compounds were identified as the previously unknown chromophoric amino acid (S)-2-amino-6-{4-[(E)-1-formyl-2-(2-furyl)ethenyl]-5-(2-furyl)-2-[(E)-(2-furyl) methylidene]-2,3-dihydro-3-oxo-1H-pyrrol-1-yl}hexanoic acid and its 2-[(Z)-(2-furyl)methylidene] isomer, by using several NMR techniques, by MS, UV, and IR spectroscopy. The identification of these novel compounds verifies the idea that melanoidin-type colorants can be generated by a cross-linking reaction between a low molecular weight chromophore and a non-coloured high molecular weight biopolymer. Received: 19 August 1997 / Revised version: 24 October 1997     

香豆素类荧光衍生试剂的合成及其柱前衍生氟虫腈HPLC-FLD检测方法的建立

以4-(二乙氨基)水杨醛为原料,经缩合成环、水解反应合成一种结构新颖的香豆素类荧光衍生试剂7-(二乙氨基)-2-氧-2H-色酮-3-羧酸（记为L1）;建立并优化L1与氟虫腈衍生化反应体系,优化后条件如下：催化缩合剂为1-(3-二甲基氨基丙基)-3-乙基碳二亚胺盐酸盐/4-二甲氨基吡啶,反应溶剂为二氯甲烷,L1与氟虫腈用量比为11∶1,反应时间为60 min,衍生温度为45 ℃;对衍生产物N-(3-氰基-1-(2,6-二氯-4-(三氟甲基)苯基)-4-((三氟甲基)亚磺酰基)-1H-吡唑-5-基)-7-(二乙氨基)-2-氧-2H-色酮-3-甲酰胺（记为SF1）进行分离和鉴定;在此基础上,建立氟虫腈柱前衍生化高效液相色谱-荧光检测方法,方法的检出限达到0.01 μg/L,定量限为0.036 μg/L。该方法具有较好的灵敏度、精确性和可靠性,可应用于农产品中氟虫腈残留的检测。