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The cyclic peptide gramicidin S was used as a rigid template to provide novel peptide-based bisphosphine ligands for transition metal catalysis. Two bisphosphine-coordinated Rh(I) complexes allowed asymmetric hydrogenation with 10-52% ee and the corresponding Pd(II) analogues catalysed asymmetric allylic alkylation with 13-15% ee.

The natural product Gramicidin S is a promising scaffold for novel oligopeptide-based bisphosphine ligands, combining the advantageous rigid chiral backbone with the close proximity of phosphine substituents. The required unnatural, phosphine-containing, amino acid building blocks were synthesized by means of a novel protocol that involves the enantioselective alkylation of a chiral nickel Schiff base template. Three Ni complexes were prepared with different alkyl chains between the phosphine group and the α-carbon atom of the incorporated glycine; the absolute stereochemistry of two of them was determined by single-crystal X-ray structure analysis. By detaching the template, enantiopure L-phosphine amino acids resulted enabling the solid-phase, stepwise construction of a linear sequence of the phosphine-modified oligopeptides. On cyclization three bisphosphine-substituted Gramicidin S analogues resulted, differing only in the size and shape of the linkage between the phosphine groups and the oligopeptides backbone. Their crystal structures suggest these species to have potential as chelating ligands. © 2009 Wiley-VCH Verlag GmbH & Co.

The synthesis of a novel carbasugar amino acid (15), starting from D‐glucose and using the Ferrier rearrangement as a key step, is reported. Compound 15 is implemented as dipeptide isostere in the synthesis of a Leu‐enkephalin analog.

A convenient method for the synthesis of functionalised 1,7-dioxaspiro[5.5]undecanes using acid-catalysed spiroketalisations of substituted dihydroxyketones is described. The dihydroxyketones were readily prepared from appropriately substituted hydroxy esters via Claisen self-condensation followed by decarboxylation.

A synthetic route towards conduramine and carbasugar derivatives based on the transformation ( i.e. two-carbon Wittig olefination and ester reduction) of the Vasella rearrangement product derived from D-galactose followed by either a [3,3] Overman or a [2,3]-Wittig-Still sigmatropic rearrangement, and subsequent ring-closing metathesis, is presented.

A stereoselective and high yielding route is described to a suitably protected derivative of (3S, 4R, 5S)-(+)-3-amino-4,5-dihydroxycyclopent-1-ene, the side chain moiety of queuosine. The synthetic route comprises a ring-closing metathesis (RCM) of a mannofuranose-derived diene followed by Overman rearrangement.

Four partially protected stereoisomeric cyclopentenetriols 5, 10, 15 and 21 have been prepared by ring-closing metathesis of carbohydrate-derived 1,6-dienes. The presence of a differentiated allylic alcohol in the cyclopentenetriols allows a variety of synthetic transformations, underlining the synthetic use of the prepared cyclopentenetriol derivatives as chiral building blocks.