(–)‐Isosteviol is readily available in large quantities by the acidic treatment of a common alternative sweetener. The two functional groups of (–)‐isosteviol are presented on the same side of the ent‐beyerane scaffold with a mutual C–C distance of about 7 Å. Their unique concave arrangement experiences a strong asymmetric environment due to an adjacent methyl group. Consequently, this building block has found several applications in supramolecular chemistry and organocatalysis. These areas and the chemical modification of this scaffold as well as its biological activity are surveyed.

SummaryThe readily available ex-chiral-pool building block (−)-isosteviol was combined with the C 3-symmetric platforms hexahydroxytriphenylene and hexaaminotriptycene providing large and rigid molecular architectures. Because of the persistent cavities these scaffolds are very potent supramolecular affinity materials for head space analysis by quartz crystal microbalances. The scaffolds serve in particular as templates for tracing air-borne arenes at low concentration. The affinities of the synthesized materials towards different air-borne arenes were determined by 200 MHz quartz crystal microbalances.

(–)‐Isosteviol is a unique ex‐chiral‐pool building block that is readily available. Both functional groups are aligned in a concave manner. The methyl moiety on the backbone also points in this direction, creating a strong asymmetric environment close to these functional groups. The slightly divergent orientation of the keto and carboxy functions limits its use in the construction of supramolecular architectures as optically pure divalent building blocks. By selective transformations, ring D of (–)‐isosteviol can be expanded and equipped with oxygen‐containing functionalities, providing a variety of useful and rigid building blocks with defined stereochemistry.

The cover picture shows the structure of (–)‐isosteviol, the functional groups of which create a kind of airfield for the interaction with other molecules, whereas the adjacent methyl tower causes an asymmetric environment. The rigid lipophilic backbone keeps this architecture, which exhibits similarities to an aircraft carrier floating on the interface. These structural features create a powerful and versatile ex‐chiral‐pool building block, which has recently found a wide application in various fields of organic chemistry. Waldvogel et al. provide a survey on (Aircraft Carrier: U.S. Navy photo by Mass Communication Specialist Seaman Iain L. Stratton, graphics C. Siering)

Review: 82 refs.