European Journal of Organic Chemistry

The elucidation of the chemical nature of chlorophyll catabolites has allowed the first structural insights into chlorophyll breakdown, assisting in developing understanding of the molecular basis and possible roles of this biological phenomenon. Current knowledge on chlorophyll catabolites in higher plants is outlined, as are their properties. Their antioxidant activity may give added value to fresh fruit.

A sequence of two aldol reactions on the dioxanone scaffold – the first one organocatalytic and the second proceeding viathe lithium enolate – allows access to higher carbohydrates and their derivatives.

Novel 3-substituted 4-indolylmaleimides have been synthesized by means of palladium-catalyzed carbonylation of 3-bromo-1-methyl-4-(2-methyl-3-indolyl)maleimide (1) with alcohols or amines in thepresence of carbon monoxide. In addition, amination of 1 proceeded smoothly in the absence of catalyst and gave the desired 3-amino-4-indolylmaleimides in good yields.

Diol and triol derivatives were glycosylated in order to prepare model compounds for the stereo- and regiochemical analysis of poly(vinyl glycoside)s. The ¹³C NMR chemical shifts of the α-C atoms of theaglycon and the anomeric C atoms exhibit a strong dependence on the absolute stereoconfiguration of the α- and the relative stereoconfiguration of the γ-C atoms, as well as the regiochemistry.

Novel star-shaped subporphyrins with monodisperse oligocarbazole arms were prepared by using pyridine-tri-N-pyrrolylborane as a template. It was found that excitation energy transfer took place from the oligocarbazole arms to the subporphyrin core.

Synthetic analogues of (2S,3R,4S)-4-hydroxyisoleucine have been prepared, mainly from D-glucose, by multi-step syntheses and evaluated for their ability to induce insulin secretion in pancreatic β-cells.

A common synthetic pathway to convert 7-oxanorbornenes into two distinct heterotricycles by selective N-allylation and subsequent domino metathesis has been developed. It is proposed that the latter reactionis guided by association of an amide carbonyl group with the Ru metal center of the catalyst. This methodology should be useful for construction of small-molecule libraries.

Resistance to penicillins is currently a major health concern. The search for non-β-lactam drugs could open new routes in the fight against bacteria. By using aminocitric acid as template, which perfectly fitsthe active site of the BS3 enzyme, we have designed phosphonic analogues and homologues for the inhibition of bacterial β-lactamases and D,D-peptidases.

Whereas sol–gel encaged Pd(OAc)₂ catalyzes Heck and Suzuki reactions in boiling benzene with the formation of metallic colloids, no detectable nanoparticles areformed when entrapped palladium derivatives of proline, tyrosine, or alanine are used to promote the coupling processes.

Prins cyclization of homoallylic alcohols with various aldehydes was investigated in ionic liquid hydrogen fluoride (HF) salts, which played roles as a reaction medium, a catalyst, and a fluorine source. The reaction afforded the corresponding 4-fluorinated tetrahydropyrans in excellent yields with a high stereoselectivity (cis form exclusively). Thia- and aza-Prins cyclization were also studied.

The ligand-free Pd(OAc)₂-catalyzed Suzuki–Miyaura C–C coupling performed in ethylene glycol monomethyl ether/H₂O at room temperature under aerobic conditions ispresented. Very fast and quantitative reactions of aryl bromides with arylboronic acids were observed with TOFs up to 180000 h^–1.

An interesting migration of the rigid structure of benzene was observed in platinum-catalyzed cyclizations of o-alkynyl(oxo)benzenes with alkenes. Various 8-oxabicyclo[3.2.1]octane derivatives with manyfunctional groups could be efficiently synthesized. The high stereo- and regioselectivity involved in this transformation was also attractive.

Self-assembly of three designer perhydro-2,3,4a,6,7,8a-naphthalenehexols, all crafted on a conformationally locked trans-decalin framework, exhibit divergent supramolecular architecture, while conforming to core concepts of O–H···O hydrogen bonding identified in the crystal structures of alcohols and sugars.

Chiral amine–polyoxometalate hybrids were found to be highly efficient and recoverable asymmetric enamine catalysts fora range of transformations with a catalyst loading as low as 0.33 mol-% under both neat and aqueous conditions.

The trans-epoxide derivative of Combretastatin A-4 was stereoselectively prepared in good yield by sulfur ylide mediated epoxidation of silyl-protected isovanillin. From this key intermediate, a formal synthesis of CA-4, by stereoselective deoxygenationand photoisomerization, was achieved. Alternatively, a trans-dioxolane derivative was obtained by stereoselective acetone insertion.

Comparative studies on the [3+2] cyclisation of N-diphenylphospinoyl and N-tosylimines with 2,3-butadienoates and 2-butynoates were performed in the presenceof (S)-tBu-binaphthophosphepine as the chiral catalyst. Enantiomerically enriched, (S)-configured N-DPP-pyrrolines were obtained in 73–92 % ee.

Tris(dialkylamino)phosphanes, formed in situ by treatment of PCl₃ with secondary amines, in conjunction with I₂ can be used to activate the C-6 amide carbonyl groups of inosine nucleosides. Subsequent displacement of hexaalkylphosphoramide by the secondary amine leads to N⁶,N⁶-disubstituted adenosine analogues. ³¹P{¹H} NMR studies were also conducted to evaluate reaction intermediates.

The syntheses of D- and L-fagomines and their isomers from starting D-glycals have been achieved. The syntheses involve elaboration of common amino alcohol precursors obtained from 2-deoxy-1-amino sugar derivatives. The key steps in the syntheses are intramolecular reductive amination and intramolecular N-heterocyclization.