Reactivity of the ester group attached isoxazoline, benzisoxazole, and isoxazole: a facial preparation of 3-acyl-substituted these heterocycles

A facile preparation of 3-acyl-substituted isoxazolines, benzisoxazoles, and isoxazoles from the corresponding 3-carboxylate esters is described. The process, involving reaction of the ester derivative of 3-carboxylic acid substituted heterocycles with Grignard or alkynyl lithium reagents, leads to direct generation of the corresponding 3-acyl heterocycle. The presence of α-imino ester moieties in the heterocyclic substrates for the reactions is thought to be a key feature governing the nature of these transformations. The synthetic utility of the new methodology is demonstrated by its application in a two-step route for the preparation of novel linked bis-heterocycles.     

Comparisons of O-acylation and Friedel-Crafts acylation of phenols and acyl chlorides and Fries rearrangement of phenyl esters in trifluoromethanesulfonic acid: effective synthesis of optically active homotyrosines

Reactions involving phenol derivatives and acyl chlorides have to be controlled for competitive O-acylations and C-acylations (Friedel-Crafts acylations and Fries rearrangements) in acidic condition. The extent for these reactions in trifluoromethanesulfonic acid (TfOH), which is used as catalyst and solvent, is examined. Although diluted TfOH was needed for effective O-acylation, concentrated TfOH was required for effective C-acylations in mild condition. These results have been applied to the novel synthesis of homotyrosine derivatives. Both Fries rearrangement of N-TFA-Asp(OBn)-OMe and Friedel-Crafts acylation of phenol with N-TFA-Asp(Cl)-OMe in TfOH afforded the homotyrosine skeleton, followed by reduction and deprotection afforded homotyrosines maintaining stereochemistry of Asp as an optically pure form.     

Applications of mapping cones over Clements–Lindström rings

We prove that Gotzmann's Persistence Theorem holds over every Clements–Lindström ring. We also construct the infinite minimal free resolution of a square-free Borel ideal over such a ring.     

Synthesis of 7‐acetyloxy‐3,7‐dimethy1‐7,8‐dihydro‐6H‐isochromene‐6,8‐dione and its analogues

7‐Alkanoyloxy‐3,7‐dimefhyl‐7,8‐dihydro‐6H‐isochromene‐6,8‐diones 12‐15 were synthesized in 69‐16% yields from the reaction of 2,4‐dihydroxy‐3‐methyl‐6‐(2‐oxopropyl)benzaldehyde 11 with p‐toluenesulfonic acid in various carboxylic acids such as acetic acid, propionic acid, butyric acid and heptanoic acid followed by oxidation with lead tetraacetate. On the other hand, (±)‐daldinin A 5 (oleate) was not obtained using oleic acid as a medium. In the cases of heptanoic acid and oleic acid, esters 16 and 17 were produced in 23 and 9% yields, respectively. 6,8‐Dihydroxy‐3,7‐dimethyl‐2‐benzopyrylium p‐toluenesulfonate 31 is considered as the intermediate for the production of 12‐15. Overall yields of isochromenes 12‐15 were 26‐6% starting from 2‐methylresorcinol for seven steps.     

Crystal structure of methyl endo-8-cyano-exo-8-methyl-3-oxo-2-oxabicyclo[2.2.2]oct-5-ene-6-carboxylate.

A photochemical cycloaddition reaction of methyl 2-pyrone-5-carboxylate with methacrylonitrile mainly gave a [4 + 2] cycloadduct, assigned as methyl endo-8-cyano-exo-8-methyl-3-oxo-2-oxabicyclo[2.2.2]oct-5-ene-6-carboxylate, whose structure was determined by an X-ray diffraction study. The formation of the cycloadduct was reasonably explained by considering a biradical intermediate having a less steric hindrance between the methoxycarbonyl group and the cyano group.     

Cepaic acid, a novel yellow xanthylium pigment from the dried outer scales of the yellow onion Allium cepa

Cepaic acid was isolated as a novel xanthylium yellow pigment from the dried outer scales of the yellow onion Allium cepa Linne. Its structure was elucidated on the basis of ESI-MS and 2D NMR spectroscopy as a 9-carboxy-1,3,6,8-tetrahydroxyxanthylium, which suggests that cepaic acid and other yellow pigments in the dried outer skin of onion were formed by the nucleophilic reaction of phloroglucinol derived from quercetin, a flavonol in onion scales, by autoxidation to glyoxylic acid. To our knowledge, this is the first report of such a pigment in yellow onion.     

Conjugated 1 beta-hydroxycholic acid in the urine of newborns and pregnant women measured by radioimmunoassay using antisera raised against N-(1 beta-hydroxycholyl)-2-aminopropionic acid-bovine serum albumin conjugate.

Anti-tauro 1 beta-hydroxycholic acid antisera were prepared by immunizing rabbits with N-(1 beta,3 alpha, 7 alpha, 12 alpha-tetrahydroxy-5 beta-cholan-24-oyl)-2- aminopropionic acid-bovine serum albumin (BSA) conjugate. The antisera raised had high affinity (1.25-1.46 x 10(9) M-1) and specificity for conjugated 1 beta-hydroxycholic acid; cross-reactivity for glyco 1 beta-hydroxycholic acid was 100% and that for the glycine and taurine conjugates of other 1 beta-hydroxylated bile acids ranged from 11.30 to 0.23%. Urinary concentrations of conjugated 1 beta-hydroxycholic acid were determined by radioimmunoassay in newborns, 0-20 d after birth, in amounts ranging from 0.29 to 18.51 micrograms/ml and in women in late pregnancy (less than 1.13 micrograms/ml), as well as in normal women (less than 0.12 microgram/ml).     

Preparation of poly(1,4-phenylene)s by electro-oxidative polymerization

The effect of substituents on the electropolymerization of benzene derivatives and the redox properrties of the corresponding polymers were determined using Brown's substituent constants (σ⁺). Electron-donating groups lower the oxidation potential by which increase in the current efficiency was observed. However, stabilization of the produced cation radicals by the electron-donating groups resulted in a decrease in the polymerization efficiency. The appropriate values of σ⁺ for the efficient polymerization ranged near ?1.5.