Generation of 6-(Trifluoromethyl)-4,5-dihydro-2(3H)-pyridone and the Application to Synthesis of Some Fused Nitrogen Heterocycles Carrying a Trifluoromethyl Group on the Bridgehead Position via Radical Cyclization of Dihydropyridones

Staudinger/aza-Wittig reaction of 6,6,6-trifluoro-5-oxohexanoyl azide with PPh(3) or PBu(3) was examined. A reactive intermediate acyl imine 1 was trapped by methanol. Without nucleophile, isomerized enamide form 3 was obtained. N-Iodobenzoylation and N-haloalkylation of 3 and following radical cyclization via the 5-exo or 6-exo mode gave benzoindolizidinone, indolizidinone, and quinolizidinone derivatives 10-14, which have a trifluoromethyl group at the bridgehead position adjacent to nitrogen. Although LiAlH(4) reduction of 10 and 11 gave a mixture of saturated benzoindolizidine 15 and amino alcohol 16, reduction with BH(3)/THF selectively gave the desired 15 and indolizidine 17 from 13.     

(−)-Daucic acid: Proof of -lyxo configuration, synthesis of its -ribo, -xylo, -arabino and -lyxo analogs, and biosynthetic implications

The dimethyl esters of the 2,6-anhydro-3-deoxy-hept-2-enaric acids with -xylo, -lyxo, -arabino, -lyxo- and -ribo-configuration were synthesized from -galactose and -mannose, respectively, and further characterized by their di-O-acetyl and di-O-benzoyl derivatives. Comparison of their physical data with those of Daucus carota derived products revealed (−)-daucic acid to have -lyxo-configuration 46 rather than the previously assigned -xylo stereochemistry 1. Dimethyl daucate 43 could be converted by acid-induced ring contraction and dehydration into naturally occurring (+)-osbeckic acid 47, thereby proving its (S)-configuration. Configurational identity in the pyranoid rings of (−)-daucic acid and KDO, together with available biosynthetic evidence on chelidonic acid 4, a leaf closing factor, suggests a joint, KDO 8-P-based pathway for their biosynthesis in plants.     

Synthesis of chitosan resin possessing 3,4-diamino benzoic acid moiety for the collection/concentration of arsenic and selenium in water samples and their measurement by inductively coupled plasma-mass spectrometry

A chitosan resin functionalized with 3,4-diamino benzoic acid (CCTS-DBA resin) was newly synthesized by using a cross-linked chitosan (CCTS) as base material. The adsorption behavior of trace amounts of elements on the CCTS-DBA resin was examined by the pretreatment with a mini-column and measurement of the elements by inductively coupled plasma-Mass spectrometry (ICP-MS). Arsenic(V) could be retained on the CCTS-DBA resin at pH 3 as an oxoanion of H₂AsO₄⁻. Selenium(VI) is strongly adsorbed at pH 2 and pH 3 as an oxoanion of SeO₄²⁻, while selenium(IV) as HSeO₃⁻ is adsorbed on the resin at pH 3. The sorption capacities are 82, 64, and 88 mg g⁻¹resin for As(V), Se(IV), and Se(VI), respectively. The effect of common anions and cations on the adsorption of As(V), Se(IV), and Se(VI) were studied; there was no interference from such anionic matrices as chloride, sulfate, phosphate, and nitrate up to 20 ppm, as well as from such artificial river water matrices as Na, K, Mg, and Ca after passing samples through the mini-column containing the resin. The CCTS-DBA resin was applied to the collection of arsenic and selenium species in bottled drinking water, tap water, and river water.     

Flow-injection spectrofluorometric determination of trace amounts of formaldehyde in water after derivatization with acetoacetanilide

A novel fluorophotometric method for formaldehyde determination in environmental waters was developed: the method does not require any enrichment procedures. A flow-injection analysis method for the spectrofluorometric determination of formaldehyde in waters, which is based on the reaction of formaldehyde with acetoacetanilide and ammonia, is proposed. The proposed method shows a good linearity from 0.50 to 40 × 10⁻⁷ M, and the limit of detection (LOD) of 3 × 10⁻⁹ M (0.09 ppb) is achievable. The sample throughput is 15 h⁻¹. One of the main advantages in the proposed method is that the reaction can be carried out at room temperature without any heating system. The effect of various interferences possibly present in the real water samples was investigated. Most cations and anions, as well as organic compounds, do not interfere with the determination of formaldehyde in environmental water samples. The proposed method is very simple, rapid, less expensive, and highly sensitive, and can be applied to the environmental water samples, such as rain, tap water and river water, at low concentration levels without any enrichment procedure.     

Conformational studies on L-serine phosphate and hydrated L-serine phosphate using ab initio SCF calculations

Ab initio MO -LCAO -SCF calculations using an STO -3G basis set were performed to find the most stable conformations of L -serine phosphate and hydrated L -serine phosphate. The most favorable conformation of L -serine phosphate is found to be one where the bond sequence O? C? C? C is trans and P? O? C? C gauche, and a very short hydrogen bond is formed between an oxygen atom of the phosphate group and a hydrogen atom of the ammonium group. For hydrated L -serine phosphate, a bridge-type hydration in which a water molecule links a phosphate oxygen and an ammonium hydrogen displays particularly low energy. In the four-hydrated L -serine phosphate anion, the most favorable conformation is such a bridged one having a rather extended configuration with regard to the bond sequences O? C? C? C and P? O? C? C.     

Antihypertensive Effect of Angiotensin‐Converting Enzyme Inhibitory Peptide Obtained from Hen Ovotransferrin

Angiotensin I‐converting enzyme (ACE) inhibitory peptide was isolated from the hen ovotransferrin hydrolysate using chymotryptic hydrolysis by two steps of reverse‐phase high‐performance liquid chromatography. The amino sequence of this novel peptide was identified as Lys‐Val‐Arg‐Glu‐Gly‐Thr‐Thr‐Tyr that inhibited ACE activity in vitro in a concentration‐dependent manner with an effective concentration (IC₅₀) of 102.8 μM. Also, this inhibition was identified as noncompetitive using the Lineweaver‐Burk plot. Moreover, the antihypertensive action of this novel peptide was investigated by an intravenous injection into spontaneously hypertensive rats (SHR). A dose‐dependent reduction of systolic blood pressure by this peptide was observed after 40 min of treatment and it decreased the blood pressure markedly at the maximal dose (1 nmol/mL/kg). The maximal blood pressure lowering activity of this peptide was calculated as 163% of captopril (10 pmol/mL/kg) that was used as positive control. In conclusion, the obtained data suggests that Lys‐Val‐Arg‐Glu‐Gly‐Thr‐Thr‐Tyr has an ability to inhibit ACE activity and decrease the systolic blood pressure in hypertensive animals.     

Palladium-catalyzed aminoallylation of activated olefins with allylic halides and phthalimide

The three-component aminoallylation reaction of the activated olefins 2 with the phthalimide 1a and allyl chloride proceeded very smoothly in the presence of Pd(2)dba(3).CHCl(3) (5 mol %)/P(4-FC(6)H(4))(3) (40 mol %) and Cs(2)CO(3) (3 equiv against 2) in dichloromethane at room temperature to give the corresponding aminoallylated products, N-pent-4-enylphthalimides 3, in 58-99% yields. The reaction of oxazolidinone 1b also proceeded very smoothly to give N-(2,2-dicyano-1-phenylpent-4-enyl)oxazolidinone in a quantitative yield; however, the Tsuji-Trost-type allylation products 4 were obtained in the case of dibenzylamine, N-tosylaniline, and pyrrolidin-2-one. Further, 2 underwent cycloaddition with N-tosylvinylaziridine 9a in the presence of Pd(2)dba(3).CHCl(3) (5 mol %)/P(4-FC(6)H(4))(3) (40 mol %) in THF at room temperature, giving the corresponding pyrrolidines 11 in 69-99% yields.