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Biomedical subjects

Siegfried Blechert

Publications and source records attributed to Siegfried Blechert.

23 records · Page 2Linked to original sources
PubMed2002

A solid-supported phosphine-free ruthenium alkylidene for olefin metathesis in methanol and water.

The synthesis and olefin metathesis activity in protic solvents of 7, a phosphine-free ruthenium alkylidene bound to a hydrophilic solid support are reported. This heterogeneous catalyst promotes relatively efficient ring closing- and cross-metathesis reactions in both methanol and water. The potential utility of homogeneous catalyst 2 for olefin metathesis in methanol is also demonstrated.

Alkenes↗
PubMed2002

A new approach to (-)-swainsonine by ruthenium-catalyzed ring rearrangement.

A new enantioselective synthesis of the idolizidine alkaloid (-)-swainsonine 1 in 40% overall yield starting from the known oxazolidinone 6 is described. Throughout the synthesis, the high efficiency of metal-catalyzed reactions is illustrated. The key step is a new ruthenium-catalyzed metathesis rearrangement reaction. In this ring-closing/ring-opening tandem process, stereocenters are transferred from a ring to the olefinic side chain of the formed heterocycle. The metathesis precursor was obtained by palladium-catalyzed desymmetrization of cyclopentenediol. The synthesis was completed by functionalization of the terminal double bond, cyclization of the second ring, and diastereoselective dihydroxylation.

Alkaloids↗
PubMed1996

[4 + 2]-Cycloaddition Reactions between beta-Acceptor-Substituted Enamines and 2-Vinylindole Radical Cations Acting as Hetero-Dienes.

[4 + 2]-Cycloaddition reactions between 2-vinylindoles acting as hetero-dienes and beta-acceptor substituted cyclic and acyclic enamines can be induced by formation of 2-vinylindole radical cations either via anodic oxidation or photoelectron transfer (PET) using catalytic amounts of triarylpyrylium tetrafluoroborates as sensitizers. In this way, pyrido[1,2-a]indoles or indolo[1,2-a]hexahydro-1,8-naphthyridines are formed in one step with complete regio- and stereochemical control.

Journal Article↗