Sieboldine A, a novel tetracyclic alkaloid from Lycopodium sieboldii, inhibiting acetylcholinesterase

[structure: see text] A novel Lycopodium alkaloid with an unprecedented fused-tetracyclic ring system consisting of an aza-cyclononane ring having a N-hydroxy group, a cyclohexanone, a cyclopentanone, and a tetrahydrofuran ring, sieboldine A (1), was isolated from the club moss Lycopodium sieboldii. The structure and relative stereochemistry were elucidated on the basis of 2D NMR data and X-ray analysis. Sieboldine A (1) exhibited a potent inhibitory activity against acetylcholinesterase and modest cytotoxicity.     

Asymmetric synthesis by the intramolecular haloetherification reaction of ene acetal: discrimination of prochiral dienes in cyclohexane systems

A novel asymmetric synthesis of the cyclohexane derivative functionalized by some substituents has been developed from the diene acetals (1), prepared from the corresponding diene aldehyde and (+)-hydrobenzoin. The treatment of 1 with NBS in the presence of MeOCH2CH2OH predominantly afforded 2 in a stereoselective manner. Subsequent alkylation of the methoxyethoxy group produced the optically active cyclohexene compounds (3) in good yields. The stereoselective chemical modification of the remaining olefin in 3 was made by OsO4-oxidation.     

Copper(I)-catalyzed substitution of propargylic carbonates with diboron: selective synthesis of multisubstituted allenylboronates

A versatile synthetic method for the preparation of the allenylboronates, Cu(I)-catalyzed reaction of propargylic carbonates with a diboron, is described. A Cu(O-t-Bu)-Xantphos catalyst system was effective for the preparation of various allenylboron compounds, allenylboronates with different substitution patterns, those with functional groups, and an axially chiral one. The Lewis acid promoted stereoselective addition to aldehydes leading to homopropargylic alcohols showed the usefulness of the new allenylboronates.     

Polarization imaging by use of optical scanning holography

Optical Review - Polarization information is useful for various applications such as remote sensing and biomedical imaging. In general, polarization information is obtained using a polarization...     

Adjacency and transition matrices related to random walks on graphs

Journal of Algebraic Combinatorics - A pointed graph $$(\Gamma ,v_0)$$ induces a family of transition matrices in Wildberger’s construction of a hermitian hypergroup using a random walk on...     

Voltage decay for lithium-excess material of Li[Li1/5Co2/5Mn2/5]O2 during cycling analyzed via backstitch method

Journal of Solid State Electrochemistry - Lithium-excess (LEX) materials of Li2MnO3?LiMO2 (M?=?Co, Ni, Fe, and so on) with large reversible capacities are promising positive...