Diffusion of dissolved ions from wet silica sol-gel monoliths: implications for biological encapsulation.

Divalent nickel (Ni(2+)), Cu(II)EDTA, methyl orange, and dichromate were used to investigate diffusion from hydrated silica sol-gel monoliths. The objective was to examine diffusion of compounds on a size regime relevant to supporting biological components encapsulated within silica gel prepared in a biologically compatible process space with no post-gelation treatments. With an initial sample set, gels prepared from tetraethoxysilane were explored in a factorial design with Ni(2+) as the tracer, varying water content during hydrolysis, acid catalyst present during hydrolysis, and the final concentration of silica.

Stereochemistry of contiguous cyclopropane formation from cascade cyclization of a skipped dienyl homoallyl triflate.

Solvolysis of asymmetric homoallylic triflates bearing a terminal stannyl substituent gives disubstituted cyclopropanes and bicyclopropanes bearing differentiated termini in high enantiopurity.

Vanadium-catalyzed selenide oxidation with in situ[2,3] sigmatropic rearrangement (SOS reaction): scope and asymmetric applications.

A vanadium-catalyzed method for the oxidation of prochiral aryl, allylic selenides with tandem [2,3] sigmatropic rearrangement has been developed. This protocol has been screened on a series of substrates to test for its generality and effectiveness. The applicability of this methodology to the synthesis of enantiomerically enriched allylic alcohols has been studied on a series of chiral oxazole-containing systems with a diastereomeric ratio (d.

Unified synthesis of C19-C26 subunits of amphidinolides B1, B2, and B3 by exploiting unexpected stereochemical differences in Crimmins' and Evans' aldol reactions.

The efficient synthesis of the C(19)-C(26) subunit of amphidinolide B(1) and B(2) has been completed using a boron-mediated aldol reaction. The synthesis of the C(19)-C(26) subunit of amphidinolide B(3) has also been accomplished through an unexpected anti aldol reaction using a titanium-mediated process. In addition, the first reported examples of a stereochemical discrepancy between the Evans' boron-mediated oxazolidinone and the Crimmins' titanium-mediated oxazolidinethione aldol reactions are disclosed.