Novel triterpenoids from the aerial roots of Ficus microcarpa

Three novel triterpenoids, 3beta-acetoxy-11alpha-hydroxy-11(12-->13)abeooleanan-12-al (1), 3beta-hydroxy-20-oxo-29(20-->19)abeolupane (2), and 29,30-dinor-3beta-acetoxy-18,19-dioxo-18,19-secolupane (3), and the known 4, 5a, and 5b were isolated from the aerial roots of Ficus microcarpa. Their structures were elucidated on the basis of 2D NMR and X-ray diffraction experiments. Compound 1, derived from the oleanane skeleton, has an unusual five-membered C ring. Compounds 2 and 3, derived from the lupane skeleton, have unique skeletons that may arise from the same biogenetic pathway.     

The first A-nor-hippuristanol and two novel 4,5-secosuberosanoids from the Gorgonian Isis hippuris

The first A-nor-hippuristanol, A-nor-22-epi-hippurin-2α-carboxylic acid (1), and two 4,5-secosuberosane sesquiterpenoids, isishippuric acids A and B (2 and 3), have been isolated from the gorgonian coral Isis hippuris. Those structures were deduced by extensive 1D and 2D NMR studies. The structure of 1 was further supported by a single crystal X-ray diffraction analysis. Isishippuric acid B has been shown to exhibit potent cytotoxicity toward a limited panel of cancer cells.     

Synthesis of Five Coordinate Spirocyclic Germanium(IV) Complexes Containing Diethanol Amine

Reaction of dihydroxo(2,2′-iminodiethanolato-AWO′) germanium(IV) (A) or dihydroxo(2,2′-methyliminodiethanolato-N,O.O′) germanium(IV) (B) with bidentate ligands, e.g. diol, α-hydroxy acid, oxalic acid, 2,6-pyridinedicarboxylic acid, or 2-aminophenol in a mixture of ethanol and xylene mixture yielded a series of unsymmetrical spiro-germanium complexes 1-6. These complexes were characterized by NMR, IR, mass spectra and elementary analysis. The ¹H NMR spectrums of all these compounds show the existence of an intramolecular N – Ge bond. X-ray analysis of compound 6 shows a short N–Ge bond (2.08 Å).     

Intense near-infrared optical absorbing emerald green [60]fullerenes

Synthesis of emerald green fullerenes (EF) C60[C(CH3)(CO2Et)2]6 and C60[C(CH3)(CO2-t-Bu)2]6 was performed by using hexaanionic C60 intermediate (C60-6) as a reagent in one-pot reaction for attaching six alkyl ester addends on one C60 cage. These EF compounds exhibit intense optical absorption over 600-940 nm, the longest optical absorption of the C60 cage among many [60]fullerene derivatives synthesized.     

Efficient epoxidation of alkenes with aqueous hydrogen peroxide catalyzed by methyltrioxorhenium and 3-cyanopyridine

The epoxidation of alkenes with 30% aqueous hydrogen peroxide is catalyzed efficiently by methyltrioxorhenium (MTO) in the presence of pyridine additives. The addition of 1-10 mol % of 3-cyanopyridine increases the system's efficiency for terminal and trans-disubstituted alkenes resulting in high isolated yields of the corresponding epoxides. The system allows for epoxidation of alkenes with various functional groups. Alkenes leading to acid-sensitive products are efficiently epoxidized using a mixture of pyridine and 3-cyanopyridine as additives. This method is operationally very simple and uses an environmentally benign oxidant. The effects of different pyridine additives on the alkene conversion and the catalyst lifetime are discussed.     

Flash Photolysis of 5-Methyl-1,4-naphthoquinone in Aqueous Solution: Kinetics and mechanism of photoenolization and of enol trapping

5-Methyl-1,4-naphthoquinone ( 1 ) is a remarkable probe to study hydrogen and proton transfer reactions. The photoenol 4-hydroxy-5-methylidene naphthalen-1 (5H)-one ( 2 ) is formed in the ground state within 2 ps of excitation and with a quantum yield of unity, presumably through a conical intersection of the S₀ and S₁ hypersurfaces. In aqueous acid, enol 2 is hydrated to 5-(hydroxymethyl)naphthalene-1,4-diol 3 (X ? OH, Scheme 1). The rate of hydration of 2 increases linearly with acid concentration from ca. 1.5 × 10⁴ s^?1 at pH 6 to reach a maximum value of 9 ×10⁷ s^?1 when the remaining carbonyl function is protonated, pK_a(2⁺) = 1.1. Contrary to an earlier suggestion, the rate-determining step in the acid-catalyzed hydration of 2 is addition of water to the conjugate acid 2 ⁺. Pronounced acceleration of the decay rate of 2 by hydrazoic-acid buffers indicates competitive trapping of 2 ⁺ by the azide ion. In neutral-to-weakly-basic solutions, enol 2 reacts by ionization, pK^a( 2 ) = 6.5, and nearly diffusion-controlled condensation of the carbanionic species 2 ^? with quinone 1 . Proto-nation at the methylidene C-atom does not compete measurably with protonation on carbonyl O-atom, despite a Substsial thermodynamic basic for carbon Portoation of ca. 50 kJ mol^?1 for 2 and 100 mol^?1 for 2^?.