The condensed tannins (syn. polymeric proanthocyanidins) represent a major group of phenolic compounds in woody and some herbaceous plants (1-3). Their exceptional concentrations in the barks and heartwoods of a variety of tree species have resulted in their commercial extraction with the initial objective of applying the extracts in leather manufacture (4). Essentially all of their biological significance, e. g. the protection of plants from insects, diseases and herbivores, and most of the current, e. g. leather manufacture, and also most promising new uses, e. g. pharmaceuticals or wood preservatives, rest on their com plexation with other biopolymers like proteins and carbohydrates, or metal ions (5, 6). Increasing attention has thus been directed to understanding their conformation and conformational flexibility (7-20) in order to explain their biological activity and to provide a basis for further development of uses for these renewable phenolic compounds. Recent developments have also been initiated by the growing realization that the condensed tannins may additionally be credited for the profound health-beneficial properties of tea, fruit juices and red wine. This is mainly due to their in vitro radical scavenging (21) or antioxidant (22) biological properties, while the polymeric proanthocyanidins in red wine have been implicated in protection against cardiovascular disorders (23), e. g. the "French paradox" (24-26). Collectively these 'positive' characteristics of the polymeric proanthocyanidins have transformed "a relatively unattractive and therefore neglected area of study" (27) into, yet again, a fashionable research field."

The chemistry of condensed tannins has hitherto represented a relatively unattractive and therefore neglected area of study; one in which the weight of research effort involved is invariably disproportionate to the results achieved, in which the participating schools generally confine their approach to specific molecular species, and in which as yet no consensus has been reached regarding likely precursors. The problems which beset those engaged in this field represent a combined function of the abnormal complexity of the gradational range of oligomers of increasing mass and affinity for substrates which typify most extracts rich in tannins, and the consequent problem of their isolation and purification, the high chirality of tannin oligomers, the need to contend with the phenomenon of dynamic 'rotational isomerism about interflavanoid bonds in the IH n.m.r. spectral interpretation of their derivatives, the lack of precise knowledge regarding the points of bonding at nucleophilic centres, and the obvious limitations of a hitherto predominantly analytical approach. The last of these reflects the need for a general method of synthesis which permits unambiguous proof of both structure and absolute configuration also at higher oligomeric levels. With these objectives in mind we initiated a purely synthetic approach based on the premise that flavan-3,4-diols as source of electrophilic flavanyl-4-carbocations, and flavan-3-0Is as nucleophiles (cf 1,2) represent the prime initiators of a process of repetitive condensation in which the immediate products also represent the sequent nucleophilic substrates.

The volumes of this classic series, now referred to simply as "Zechmeister" after its founder, L. Zechmeister, have appeared under the Springer Imprint ever since the series inauguration in 1938. The volumes contain contributions on various topics related to the origin, distribution, chemistry, synthesis, biochemistry, function or use of various classes of naturally occurring substances ranging from small molecules to biopolymers. Each contribution is written by a recognized authority in his field and provides a comprehensive and up-to-date review of the topic in question. Addressed to biologists, technologists, and chemists alike, the series can be used by the expert as a source of information and literature citations and by the non-expert as a means of orientation in a rapidly developing discipline.

Published to mark the artist's first solo US museum show, Paulo Nazareth: Melee presents an engaging and timely look at the artist's multifarious work. The exhibition, held at the Institute of Contemporary Art, Miami in 2019, explored how Nazareth's work engages the complex colonial and racial histories of the Americas. An artist who works across mediums, Nazareth uses performance and sculpture to critique the colonial experience and its afterlives in Brazil and the Americas. His durational performances and installations draw from his joint African and Indigenous heritage to highlight marginalized historical legacies, progressive political figures, non-Western worldviews, and potential methods of nonexploitative living and relating. Nazareth's work assumes a new poignancy in light of the return of repressive political forces and the racial reckoning that our historical moment demands. This beautifully produced volume offers over one hundred color illustrations in addition to newly commissioned scholarship. Paulo Nazareth: Melee is the first exhaustive catalogue of Nazareth's work, solidifying his place as one of today's most important global artists.