Efficient synthesis of aminomethylated azaindoles and corresponding pyrrole-fused derivatives by copper-catalyzed domino multicomponent coupling and cyclization

Efficient methods for the synthesis of aminomethylated azaindole derivatives via domino copper-catalyzed multicomponent coupling and cyclization have been developed. Using various secondary amines and aldehydes, N-substituted 3-ethynyl-4-aminopyridine was converted to substituted azaindoles in moderate to excellent yields. By use of a 3,4-diaminopyridine derivative bearing two alkynyl groups, the corresponding pyrrole-fused azaindoles were synthesized by controlled stepwise cyclization.     

Synthesis of polymers by template polymerization. I. Template polymerization of poly(methacrylic acid) with β‐cyclodextrin

A novel template monomer with multiple methacryloyl groups was synthesized with β‐cyclodextrin by the acetylation of primary hydroxyl groups and the esterification of secondary hydroxyl groups with methacrylic acid anhydride. The average number of methacryloyl groups in the monomer was 11. The radical polymerization of the monomer was carried out with the following initiators: α,α′‐azobisisobutylonitrile, H₂O₂? Fe²⁺ redox initiator, p‐xylyl‐N,N‐dimethyldithiocarbamate (XDC), and α‐bromo‐p‐xylyl‐N,N‐dimethyldithiocarbamate (BXDC). When the concentration of the monomer was less than 4.12 × 10^?3 M, polymerization was limited inside the molecule, and gelation of the system was hindered. For controlled radical photopolymerization with XDC and BXDC, the methacryloyl groups of the monomer were homogeneously polymerized, and poly(methacrylic acid) with a narrow molecular weight distribution was obtained by the hydrolysis of the polymerized products. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3539–3546, 2001     

KINETICS AND MECHANISM OF PHOTOCYCLOADDITION OF DEOXYURIDINES TO 2,3-DIMETHYL-2-BUTENE

The mechanism of photocycloaddition of 2′-deoxyuridine (1a) and thymidine (1b) to 2,3-dimethyl-2-butene (Bu) in acetonitrile by UV irradiation has been studied. The reciprocal quantum yield for the cycloaddition increased linearly with reciprocal concentrations of Bu in acetonitrile to give limiting quantum yields at infinite concentration of Bu as 0.030 and 0.0096 for 1a and 1b , respectively. This shows that the cycloaddition proceeds in a two-step mechanism between the triplet state of 1 and Bu through biradical intermediates. Addition of cis-1,3-pentadiene quenched the reaction obeying the Stern–Volmer equation. The above quenching experiments and laser transient spectroscopy revealed that the triplet state of 1a reacts with Bu with much larger rate constant (1.3–1.6 × 10⁹ M^?1 s^?1) than that of 1b (4–5 × 10⁷ M^?1 s^?1) reflecting larger steric hindrance exerted in the reaction of 1b than that of 1a .     

Photothermal Oxidation of Cinnamyl Alcohol with Hydrogen Peroxide Catalyzed by Gold Nanoparticle/Antimony-Doped Tin Oxide Nanocrystals

Gold nanoparticles with different mean sizes were formed on antimony-doped tin oxide nanocrystals by the temperature-varied deposition-precipitation method (Au/ATO NCs). Au/ATO NCs possess strong absorption in the near-infrared region due to Drude excitation in addition to the localized surface plasmon resonance (LSPR) of AuNPs around 530 nm. Au/ATO NCs show thermally activated catalytic activity for the oxidation of cinnamyl alcohol to cinnamaldehyde by hydrogen peroxide. The catalytic activity increases with a decrease in the mean Au particle size (d_Au) at 5.3 nm≤d_Au≤8.2 nm. Light irradiation (λ_ex >660 nm, ∼0.5 sun) of Au/ATO NCs increases the rate of reaction by more than twice with ∼95 % selectivity. Kinetic analyses indicated that the striking enhancement of the reaction stems from the rise in the temperature near the catalyst surface of ∼30 K due to the photothermal effect of the ATO NCs.     

2 alpha-(3-hydroxypropyl)- and 2 alpha-(3-hydroxypropoxy)-1 alpha,25-dihydroxyvitamin D3 accessible to vitamin D receptor mutant related to hereditary vitamin D-resistant rickets

Hereditary vitamin D-resistant rickets (HVDRR) is a genetic disorder caused by mutations in the vitamin D receptor, which lead to resistance to 1alpha,25-dihydroxyvitamin D(3) [1alpha,25(OH)(2)D(3)]. We found that the A ring-modified analogues, 2alpha-(3-hydroxypropyl)- and 2alpha-(3-hydroxypropoxy)-1alpha,25(OH)(2)D(3), (O1C3 and O2C3) can bind better than the natural hormone to the mutant VDR (R274A), which similar to the HVDRR mutant, R274L, had lost the hydrogen bond to the 1alpha-hydroxyl group of 1alpha,25(OH)(2)D(3).     

An efficient fluorescence sensor for superoxide with an acridinium ion-linked porphyrin triad

Addition of potassium superoxide with 18-crown-6 ether (KO(2)(?-)-18-crown-6) to a toluene solution of an acridinium ion-linked porphyrin triad (Acr(+)-H(2)P-Acr(+)) resulted in a remarkable enhancement of the fluorescence intensity. Thus, Acr(+)-H(2)P-Acr(+) acts as an efficient fluorescence sensor for superoxide. Electron transfer from KO(2)(?-)-18-crown-6 to the Acr(+) moiety to produce the two-electron-reduced species (Acr(?)-H(2)P-Acr(?)) results in inhibition of the fluorescence quenching via photoinduced electron transfer, as revealed by laser flash photolysis measurements.     

Cupric superoxo-mediated intermolecular C-H activation chemistry

The new cupric superoxo complex [LCu(II)(O(2)(?-))](+), which possesses particularly strong O-O and Cu-O bonding, is capable of intermolecular C-H activation of the NADH analogue 1-benzyl-1,4-dihydronicotinamide (BNAH). Kinetic studies indicated a first-order dependence on both the Cu complex and BNAH with a deuterium kinetic isotope effect (KIE) of 12.1, similar to that observed for certain copper monooxygenases.     

Enzymatic Synthesis and Polymerization of Cyclic Trimethylene Carbonate Monomer with/without Methyl Substituent

The direct enzymatic synthesis of a cyclic trimethylene carbonate (1,3‐dioxane‐2‐one) monomer with/without a methyl substituent was carried out using dimethyl or diethyl carbonate and 1,3‐diol with the objective of producing aliphatic poly(trimethylene carbonate), a typical biodegradable synthetic plastic. The lipase‐catalyzed condensation of dimethyl or diethyl carbonate with aliphatic 1,3‐diols using immobilized Candida antarctica lipase (lipase CA) in an organic solvent at 70 °C afforded the corresponding methyl‐substituted and unsubstituted cyclic trimethylene carbonates. The cyclic trimethylene carbonates obtained by the reaction of dimethyl or diethyl carbonates with 1,3‐propanediol and 2‐methyl‐1,3‐propanediol were polymerized by lipase to produce the corresponding polycarbonates.

Total TMC yield as a function of the reaction time.     

Efficient synthesis of 2-modified 1alpha,25-dihydroxy-19-norvitamin D3 with Julia olefination: high potency in induction of differentiation on HL-60 cells

Six novel 2-substituted analogues of 1alpha,25-dihydroxy-19-norvitamin D(3), 6a,b-8a,b, were efficiently synthesized utilizing (-)-quinic acid as the A-ring precursor. The C2-modified A-rings were prepared as 4-alkylated (3R,5R)-3,5-dihydroxycyclohexanones 12-15 from (-)-quinic acid based on radical allylation at the C4 position of methyl (-)-quinicate. The new type of the CD-ring coupling partner 23 was synthesized from 25-hydroxy Grundmann's ketone 19 to apply to the modified Julia olefination to construct a diene unit between the A-ring and the CD-ring. The coupling yields, including a deprotection step, were 47-62%. After the separation of the diastereomers based on C2 stereochemistry, the structure (2alpha or 2beta) was determined by (1)H NMR experiments and compared to DeLuca's 2-methyl- and 2-ethyl-1alpha,25-dihydroxy-19-norvitamin D(3). Thus, the synthesized 2alpha-(3-hydroxypropyl)-1alpha,25-dihydroxy-19-norvitamin D(3) (8a) showed almost the same potency in binding to the bovine thymus vitamin D receptor (VDR) as the natural hormone 1, while its beta-isomer 8b had only a 3% affinity. Both 2alpha-allyl- and 2alpha-propyl-1alpha,25-dihydroxy-19-norvitamin D(3) (6a and 7a) and their 2beta-analogues (6b and 7b) possessed a weak affinity for the VDR. The strong VDR ligand 8a was ca. 36-fold more potent in induction of HL-60 cell differentiation than 1, and interestingly, even the weaker ligand 8b showed a 6.7-fold higher potency in the cell differentiation activity than that of 1.     

Total Synthesis of Hydroxy-α- and Hydroxy-β-sanshool Using Suzuki-Miyaura Coupling

Here, we describe the first total synthesis of hydroxyl-α- and hydroxyl-β-sanshool, which involves Suzuki-Miyaura coupling (SMC). Hydroxy-α-sanshool (1) was synthesized by SMC of bromoalkyne 4 with boronate 3 followed by (Z)-selective reduction of the triple bond in the coupling product. Hydroxy-β-sanshool (2) was synthesized by regio- and (E)-selective conversion of 4 to iodoalkene 11 followed by SMC with 3.