Determination of Chlorinated Hydrocarbon Species in Aqueous Solution Using Teflon Coated ATR Waveguide/FTIR Spectroscopy

The potential of an optical sensor based on mid-infrared spectroscopy, utilising a zinc selenide (ZnSe) attenuated total reflectance (ATR) element coated with an amorphous Teflon polymer, to determine chlorinated hydrocarbon species (CHC) in an aqueous environment is examined. The polymer coating concentrates the analytes within the penetration depth of the Fourier transform infrared (FTIR) evanescent wave and excludes water from the region. Teflon AF (Amorphous Fluoropolymer) is a family of amorphous copolymers based on polytetrafluoroethylene (PTFE), and is commercially available in two polymeric grades. Teflon AF is highly amorphous in nature with a large 'void volume', exhibits excellent chemical resistance and low water absorption. Such properties identify it as an excellent candidate for enrichment coating on an ATR/FTIR sensor. The potential of both polymeric grades of Teflon AF as enrichment membranes for ATR/FTIR analysis of CHC species was examined and contrasted. A rapid, repeatable, reversible response was observed with both grades to a range of CHC species. Linear responses in the mg/L region, with detection limits in the low mg/L region were achieved with the system used.     

Gram-scale synthesis of anti-pancreatic flavonoids (±)-8-[1-(4′-hydroxy-3′-methoxyphenyl)prop-2-en-1-yl]-chrysin and -galangin

Gram-scale total synthesis of (±)-8-[1-(4′-hydroxy-3′-methoxyphenyl)prop-2-en-1-yl]-galangin (1) and -chrysin (2) has been accomplished in eight steps from commercially available phloroglucinol and three steps from commercially available chrysin, respectively, featuring an efficient introduction of C(8) (1-prop-2-en-1-yl)phenyl moiety in the natural products through chemo- and regioselective cinnamylation and regioselective aromatic Claisen rearrangement.     

Total synthesis of methyl l-daunosaminide hydrochloride via chiral 1,3-oxazine

Total synthesis of methyl l-daunosaminide hydrochloride was achieved from readily available l-tyrosine. Key steps in this strategy were palladium(0) catalyzed stereoselective intramolecular oxazine formation and catalytic hydrogenation of oxazine intermediate. This paper reported ¹H and ¹³C NMR data of α- and β-anomer of methyl l-daunosaminide hydrochloride.     

Total synthesis of Daphnodorin A

A total synthesis of Daphnodorin A, a member of the Daphnodorins, was accomplished. Key features of the synthetic strategy include construction of 2-substituted-3-functionalized benzofuran via intramolecular Heck reaction and a mild Barton–McCombie deoxygenation process mediated by triethylborane. The total synthesis provided Daphnodorin A in 19.7% or 5.6% overall yield over 7 or 15 steps.     

Total synthesis of unsaturated imine venom alkaloids of Costa Rican ant by way of Schmidt reaction via allyl/pentadienyl cations

Total synthesis of α,β-, and α,β,γ,δ-unsaturated imine ant venom alkaloids is described. The labile two conjugated imine alkaloids were synthesized by late stage intramolecular Schmidt reaction via allyl and pentadienyl cation intermediates.     

Stereoselective synthesis of the right-hand segment of tubiferal A

Tubiferal A, a triterpenoid isolated from myxomycete Tubifera dimorphotheca, exhibits a reversal effect of vincristine (VCR) resistance against VCR-resistant KB cell lines. The compound possesses a complex structure involving the 6-7-6-5 polycyclic carbon framework with various functional groups. The stereoselective synthesis of the right-hand segment of tubiferal A was achieved on the basis of the cyclopentene annulation method and the semi-pinacol rearrangement reaction of an epoxy alcohol for constructing the trans-fused 6-5 bicyclic skeleton possessing two quaternary carbon atoms at the angular positions.     

Total synthesis of (6Z,9S)-3,4-trans-9-hydroxy-3-methyldodec-cis-6-en-4-olide and (6Z)-3,4-trans-9-oxo-3-methyldodec-cis-6-en-4-olide γ-butyrolactones

The first total synthesis of (6Z,9S)-3,4-trans-9-hydroxy-3-methyldodec-cis-6-en-4-olide and (6Z)-3,4-trans-9-oxo-3-methyldodec-cis-6-en-4-olide was achieved in a convergent pathway. The salient features of our synthesis include Ohira–Bestmann reaction, regioselective alkyne addition to terminal epoxide, TEMPO/BAIB mediated oxidative lactonization, and partial hydrogenation.     

Asymmetric synthesis of the four stereoisomers of 5-deoxystrigol

Two approaches to the strigolactone tricyclic lactone skeleton 2 were investigated using ketene/ketene-iminium cycloaddition to olefins. Finally, the first enantioselective access to the four stereoisomers of 5-deoxystrigol 1 is reported using an intramolecular [2+2] cycloaddition of homochiral ketene-iminium salts 5. Very high asymmetric control was achieved with C-2 symmetric pyrrolidines as chiral auxiliary.     

Synthetic studies directed toward the AB decalin common to HMP-Y1 and hibarimicinone

Efforts toward the synthesis of the decalin ring system common to the hibarimicin shunt metabolite HMP-Y1 and parent aglycone hibarimicinone are reported herein. An intramolecular Diels–Alder cyclization rapidly generated the decalin framework. Two approaches toward completion of the AB decalin were vetted. Incorporation of a phenylsulfonyl leaving group β- to both a ketone and a γ-lactone followed by base-induced elimination of sulfinate led to the undesired α,β-unsaturated lactone. Methanolysis of the γ-lactone followed by elimination produced the unexpected bridged cyclic ether by way of an intramolecular oxy-Michael addition of the endo oriented C13 alcohol.