Selective Synthetic Reactions Applying Neighboring Group Participation.

Observation of neighboring ortho-hydroxyl group participation in organocatalytic asymmetric sequential Michael-lactonization reactions: synthesis of highly substituted chiral spirodihydrocoumarins.

A general approach to asymmetric synthesis of highly substituted spirodihydrocoumarins with a quaternary stereocenter was achieved through neighboring ortho-hydroxyl group induced sequential Michael-lactonization reactions on 2-(2-nitrovinyl)phenols with alkyl cyclopentanone-2-carboxylates in the presence of a catalytic amount of quinine-NH-thiourea followed by p-TSA.

Access to oxetane-containing psico-nucleosides from 2-methyleneoxetanes: a role for neighboring group participation?

The first psico-oxetanocin analogue of the powerful antiviral natural product, oxetanocin A, has been readily synthesized from cis-2-butene-1,4-diol. Key 2-methyleneoxetane precursors were derived from β-lactones prepared by the carbonylation of epoxides. F(+)-mediated nucleobase incorporation provided the corresponding nucleosides in good yield but with low diastereoselectivity. Surprisingly, ...

Neighboring-group participation by C-2 ether functions in glycosylations directed by nitrile solvents.

Ether-protecting functions at C-2 hydroxy groups have been found to play participating roles in glycosylations when the reactions are conducted in nitrile solvent mixtures. The participation mechanism is based on intramolecular interaction between the lone electron pair of the oxygen atom of the C-2 ether function and the nitrile molecule when they are positioned in a cis configuration. A 1,2-c...

Neighboring carboxyl group participation in the hydrolysis of monoesters of phthalic acid. The dependence of mechanisms on leaving group tendencies.

Alignments of Group Galaxies with Neighboring Groups

Using a sample of galaxy groups found in the Sloan Digital Sky Survey Data Release 4, we measure the following four types of alignment signals: (1) the alignment between the distributions of the satellites of each group relative to the direction of the nearest neighbor group (NNG); (2) the alignment between the major axis direction of the central galaxy of the host group (HG) and the direction ...