Panacea for aldol desymmetrizations : We describe an easy entry for the desymmetrization of 4‐substituted‐cyclohexanones catalyzed by proline, using as cocatalysts different hydrogen‐bonding donors (see scheme), which dramatically improves the catalytic efficiency of proline in desymmetrization reactions.
Meeting the demand for sugars : The importance of oligosaccharides and glycoconjugates in biological systems has stimulated a need to access significant amounts of these compounds. Much effort has been devoted to the stereoselective generation of the key glycosidic bond, both between carbohydrate residues (see scheme) and to the aglycone. Various methodologies are now available for the efficient synthesis of structurally defined complex oligosaccharides and glycoconjugates.
Extension ladder : The successful application of epoxide‐opening strategies towards the synthesis of ladder‐type polyethers is contingent upon further elaboration of the product. By employing two different functionalized templates, a fragment of gymnocin A that bears four sites for subsequent fragment coupling has been prepared (see scheme; Bn=benzyl).
Spiders of the genus Argiope , such as Argiope lobata, contain polyamine toxins that are potent but nonselective blockers of glutamate receptors. However, by very subtle modifications of the structure of native toxins, it is possible to obtain selectivity for subtypes of these receptors, as described by K. Strømgaard and co‐workers in their Communication on page 3087 ff.
Roll up : A peptide–dendron hybrid (PDH) is capable of self‐assembling into either a soluble nanotube or an amyloid‐like fibrillar network. The structures interconvert on adjusting the salt concentration or pH value. Their hydrophobic interfaces efficiently encapsulate hydrophobic molecules in water which can then be released by lowering the pH value.
Electron disco: A “quantum stroboscope” for capturing the electron motion on a subfemtosecond timescale for a particular class of problems is highlighted. The picture shows a diffraction pattern caused by wave packets obtained by synchronizing attosecond UV pulses to a near‐IR field and ionizing rare‐gas atoms.
