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A unique π-expanded reaction cavity tethering a polycyclic moiety which provides a platform for substrate binding was constructed within the robust β-barrel structure of nitrobindin (NB). NB variants with cavities of different sizes and shapes are coupled with N-(1-pyrenyl)maleimide ( Pyr) to prepare a series of NB- Pyr conjugates. The orientation of the pyrene moiety is fixed within the cavity by the coupling reaction. The fluorescent quenching analysis of NB- Pyr indicates that azachalcone ( aza), which is a dienophile for a Diels-Alder (DA) reaction, is efficiently incorporated within the pyrene-linked reaction cavity by the aromatic interaction. The DA reaction between aza and cyclopentadiene proceeds within the reaction cavity of NB- Pyr in the presence of CuII ion in high yield and high enantio- and regioselectivity. [ABSTRACT FROM AUTHOR]

Ein Pyren‐verknüpfter Proteinhohlraum zieht zwei Substratmoleküle an – ungefähr so wie der Duft einer Blume Schmetterlinge anlockt. A. Onoda, T. Hayashi und Mitarbeiter demonstrieren in ihrer Zuschrift auf S. 13806, dass eine polycyclische Pyrengruppe, die an das starre Proteingerüst der β‐Fass‐Struktur von Nitrobindin geknüpft ist, aromatische Wechselwirkungen mit einem Substrat bereitstellt. Eine asymmetrische Diels‐Alder‐Reaktion zwischen Azachalkon und Cyclopentadien verläuft glatt mit hoher Stereoselektivität innerhalb des Reaktionsgerüsts. [ABSTRACT FROM AUTHOR]

A pyrene‐linked protein cavity attracts two substrate molecules like the scent of a flower attracts butterflies. In their Communication on page 13618 ff., A. Onoda, T. Hayashi, and co‐workers demonstrate that a polycyclic pyrene moiety linked within the rigid protein scaffold of the β‐barrel of nitrobindin acts as a platform to provide an aromatic interaction with a substrate. An asymmetric Diels–Alder reaction between azachalcone and cyclopentadiene proceeds smoothly with high stereoselectivity within the reaction scaffold. [ABSTRACT FROM AUTHOR]