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The fall colors are signs of chlorophyll breakdown, the biological process in plants that generates phyllobilins. Most of the abundant natural phyllobilins are colorless, but yellow phyllobilins (phylloxanthobilins) also occur in fall leaves. As shown here, phylloxanthobilins are unique four-stage photoswitches. Which switching mode is turned on is controlled by the molecular environment. In polar media, phylloxanthobilins are monomeric and undergo photoreversible Z/ E isomerization, similar to that observed for bilirubin. Unlike bilirubin, however, the phylloxanthobilin Z isomers photodimerize in apolar solvents by regio- and stereospecific thermoreversible [2+2] cycloadditions from self-assembled hydrogen-bonded dimers. X-ray analysis revealed the first stereostructure of a phylloxanthobilin and its hydrogen-bonded self-templating architecture, helping to rationalize its exceptional photoswitch features. The chemical behavior of phylloxanthobilins will play a seminal role in identifying biological roles of phyllobilins. [ABSTRACT FROM AUTHOR]

Described herein is a general and mild catalytic asymmetric 1,6-conjugate addition of para-quinone methides ( p-QMs), a class of challenging reactions with previous limited success. Benefiting from chiral Brønsted acid catalysis, which allows in situ formation of p-QMs, our reaction expands the scope to general p-QMs with various substitution patterns. It also enables efficient intermolecular formation of all-carbon quaternary stereocenters with high enantioselectivity. [ABSTRACT FROM AUTHOR]

One hundred years after his Nobel Prize, Richard Willstätter’s achievements and the fascinating role he played in 20th century chemistry are discussed in this Essay. Several of his discoveries, such as the anthocyanidins, cyclooctatetraene, the ortho‐quinones, and the structure of cocaine, will forever be associated with his name. [ABSTRACT FROM AUTHOR]

The inside cover of the December 2016 issue of the journal "Angewandte Chemie International Edition" is presented.