Biomedical subjects

Volker Berl

Publications and source records attributed to Volker Berl.

5 recordsLinked to original sources

PubMed2006

Selective product amplification of thymine photodimer by recognition-directed supramolecular assistance.

Two symmetric ditopic supramolecular templates (1 and 2) each presenting two hydrogen bonding recognition subunits were synthesized. Each such subunit comprises the same donor and acceptor pattern, capable of binding a substrate molecule with complementary hydrogen bonding groups to form a supramolecular complex. Substrate molecules, such as thymine or uracil derivatives, yield 2 : 1 complexes with the acceptors involving two hydrogen bonds to each subunit with ideal orientation for subsequent [2 + 2] dimerization upon photoirradiation. Selective syn photoproduct formation and concomitant suppression of the trans isomer are favored by orientation of the two guest nucleobases within the template cleft. Complementary donor and acceptor hydrogen bonding induced positioning of the two substrates and steric hindrance within the template clefts are responsible for the selective product formation.

Catalysis↗

PubMed2005

An improved synthesis of the "miracle nutrient" coenzyme Q10.

[reaction: see text] A new route to the key coupling partner, chloromethylated CoQ0 (1), allows for direct formation of CoQ10 (3) via nickel-catalyzed cross-coupling with the side chain in the form of an in situ-derived vinyl alane (2).

Alkenes↗

PubMed2003

Contraction/extension molecular motion by protonation/deprotonation induced structural switching of pyridine derived oligoamides.

NMR, mass spectrometry and X-ray diffraction studies show reversible structural interconversion between helical and extended forms of pyridine derived oligoamide molecular strands, by simple protonation/deprotonation.

Journal Article↗

PubMed2002

Chemo-, regio-, and enantioselective Pd-catalyzed allylic alkylation of indolocarbazole pro-aglycons.

[reaction: see text] Monosubstituted isomerically pure indolopyrrolocarbazole precursors have been prepared via palladium-catalyzed asymmetric allylic alkylation methodology, employing both achiral cyclopentenyl electrophiles and chiral glycal derivatives. Chemoselective allylation of (bis)indole lactam pro-aglycon 3 allows access to N-distally substituted indolopyrrolocarbazole derivatives; glyoxamide precursor 14 provides entry into N-proximally substituted derivatives.

Alkylation↗

PubMed2002

Supramolecular polymers generated from heterocomplementary monomers linked through multiple hydrogen-bonding arrays--formation, characterization, and properties.

Supramolecular polymers are described that are derived from the association of two homoditopic heterocomplementary monomers through sextuple hydrogen-bonding arrays. They form fibers and a variety of different materials depending on the conditions. The strong affinity of the DAD-DAD (D=donor, A=acceptor) hydrogen-bonding sites for double-faced cyanuric acid type wedges drives the supramolecular polymeric assembly in apolar and chlorinated organic solvents. The marked influence of stoichiometry, as well as end-capping and cross-linking agents upon fiber formation is revealed in solution and by electron microscopy (EM). The results further contribute to the development of a supramolecular polymer chemistry that comprises reversible polymers formed through recognition-controlled noncovalent connections between the molecular components. Such materials are, by nature, dynamic and present adaptive character in view of their ability to respond to external stimuli.

Chemical Phenomena↗