Hyperfine interactions of muonium and hydrogen in silicon and diamond: Quantum chemical calculations

The electronic structure of a hydrogen-like atom located at interstitial sites of the silicon and diamond crystals is calculated by the intermediate neglect of differential overlap (INDO) method. Calculations of the electronic g- and hyperfine interaction tensors of the impurity atom are performed. The results obtained are compared with the experimental properties of both “anomalous” muonium and hydrogen centers. It is shown that the most likely model for these centers in silicon and diamond is that in which interstitial neutral hydrogen-like atom locates at the bond-center site.     

Physovenines: Efficient Synthesis of (−)- and (+)-Physovenine and Synthesis of Carbarnate Analogues of (−)-Physovenine. Anticholinesterase Activity and Analgesic Properties of Optically Active Physovenines

Column chromatography of easy available (±)-physovenine ( 2 ) on cellulose triacetate afforded (?)- and (+)-physovenine ( 2a and 2b , resp.). Alkaloids 2a , b required for pharmacological testing were prepared from eserolincs ( 3a , b ) by an improved procedure. Natural (?)-physovenine ( 2a ) was equally potent in inhibiting AChE and BChE in vitro as natural physostigmine (1a), and twice as potent as the unnatural antipode 2b against AChE and 14 times as potent against BChE. Several carbamate analogs of 2a were at least as potent as the former compound in these assays. None of the compounds tested did bind to different opiate receptor or serotonine receptor preparations. Most of the compounds tested had considerable analgesic activity in the Writhing test.     

Hydroxylated pyrrolidines. Enantiospecific synthesis of all-cis 2,3,4,5-substituted pyrrolidine derivatives from serine

We report the enantiospecific synthesis of the sterically congested all-cis 2,3,4,5-substituted pyrrolidines 4, 5, and 6, from either D- or L-serine. Hemiaminal intermediate 13 is converted to the fully substituted pyrrolidine 15 by way of a tandem Wittig-Michael reaction. The endo stereochemistry of the C-3 methyl group of compound 15 is set by stereoselective reduction of the double bond in 11, driven by a preference for hydrogenation from the rear side of the molecule. The all-cis configuration of these fully substituted pyrrolidines has been established by X-ray analysis of compound 6. Removal of the benzenesulfonyl group from the highly substituted and functionalized intermediate 15 is successfully accomplished by sodium naphthalenide reduction.