Magnetic circular dichroism studies—XLVI: Structure and the magnetic circular dichroism of trans-2-decalones and bicyclo[2.2.2]octan-2-ones

The magnetic CD spectra of a number of Me substituted trans-2-decalones and bicyelo[2.2.2]octan-2-ones were measured. The results showed a large, and sometimes dominant, contribution to the MCD intensity which could be correlated with the presence of α-substituents lying outside of the plane of the carbonyl chromophore.     

Sign changes in the prime number theorem

The Ramanujan Journal - Let V(T) denote the number of sign changes in $$\psi (x) - x$$ for $$x\in [1, T]$$ . We show that $$\liminf _{T\rightarrow \infty } V(T)/\log T\ge \gamma _{1}/\pi +...     

Organocatalytic functionalization of carboxylic acids: isothiourea-catalyzed asymmetric intra- and intermolecular Michael addition--lactonizations

Tetramisole promotes the catalytic asymmetric intramolecular Michael addition-lactonization of a variety of enone acids, giving carbo- and heterocyclic products with high diastereo- and enantiocontrol (up to 99:1 dr, up to 99% ee) that are readily derivatized to afford functionalized indene and dihydrobenzofuran carboxylates. Chiral isothioureas also promote the catalytic asymmetric intermolecular Michael addition-lactonization of arylacetic acids and α-keto-β,γ-unsaturated esters, giving anti-dihydropyranones with high diastereo- and enantiocontrol (up to 98:2 dr, up to 99% ee).     

Identification of a set of genes showing regionally enriched expression in the mouse brain

Background

We have recorded responses from single neurons in murine visual cortex to determine the effectiveness of the input from the two murine cone photoreceptor mechanisms and whether there is any unique selectivity for cone inputs at this higher region of the visual system that would support the possibility of colour vision in mice. Each eye was stimulated by diffuse light, either 370 (strong stimulus for the ultra-violet (UV) cone opsin) or 505 nm (exclusively stimulating the middle wavelength sensitive (M) cone opsin), obtained from light emitting diodes (LEDs) in the presence of a strong adapting light that suppressed the responses of rods.

Results

Single cells responded to these diffuse stimuli in all areas of striate cortex. Two types of responsive cells were encountered. One type (135/323 – 42%) had little to no spontaneous activity and responded at either the on and/or the off phase of the light stimulus with a few impulses often of relatively large amplitude. A second type (166/323 – 51%) had spontaneous activity and responded tonically to light stimuli with impulses often of small amplitude. Most of the cells responded similarly to both spectral stimuli. A few (18/323 – 6%) responded strongly or exclusively to one or the other spectral stimulus and rarely in a spectrally opponent manner.

Conclusion

Most cells in murine striate cortex receive excitatory inputs from both UV- and M-cones. A small fraction shows either strong selectivity for one or the other cone mechanism and occasionally cone opponent responses. Cells that could underlie chromatic contrast detection are present but extremely rare in murine striate cortex.     

Synthesis of 4-arylpiperidines from 1-benzyl-4-piperidone: application of the Shapiro reaction and alkenylsilane cross-coupling

[reaction: see text] 1-Benzyl-3,4-unsaturated-4-piperidinyl benzyldimethylsilane has been prepared and observed to readily undergo palladium-catalyzed cross-coupling reactions with a variety of aryl iodides and aryl bromides to generate 3,4-unsaturated 4-arylpiperidines, often at ambient temperature.     

Rhenium-catalyzed 1,3-isomerization of allylic alcohols: scope and chirality transfer

The scope of the triphenylsilyl perrhennate (O3ReOSiPh3, 1) catalyzed 1,3-isomerization of allylic alcohols has been thoroughly explored. It was found to be effective for a wide variety of secondary and tertiary allylic alcohol substrates bearing aryl, alkyl, and cyano substituents. Two general reaction types were found which gave high levels of product selectivity: those driven by formation of an extended conjugated system and those driven by selective silylation of a particular isomer. The efficiency of chirality transfer with various substrates was investigated, and conditions were found in which secondary and tertiary allylic alcohols could be formed with high levels of enantioselectivity. Consideration of selectivity trends with respect to the nature of the substituents around the allylic system revealed that this is a reliable and predictable method for allylic alcohol synthesis.