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Bredt's rule holds a special place in the realm of physical organic chemistry, but its application to natural products chemistry-the field in which the rule was originally formulated-is not well defined. Herein, the use of olefin strain (OS) energy as a readily calculated predictor of the stability of natural products containing a bridgehead alkene is introduced. Schleyer first used OS energies to classify parent bridgehead alkenes into 'isolable', 'observable', and 'unstable' classes. OS calculations on natural products, using contemporary forcefield methods, unequivocally predict all structurally verified bridgehead alkene natural products to be 'isolable'. Thus, when one assigns the structure of a putative bridgehead alkene natural product, an OS in the 'observable' or 'unstable' ranges is a red flag for error. [ABSTRACT FROM AUTHOR]

Well over a hundred years ago, Professor Julius Bredt embarked on a career pursuing and critiquing bridged bicyclic systems that contained ring strain induced by the presence of a bridgehead olefin. These endeavors founded what we now know as Bredt's rule (Bredtsche Regel). Physical, theoretical, and synthetic organic chemists have intensely studied this premise, pushing the boundaries of such systems to arrive at a better understood physical phenomenon. Mother nature has also seen fit to construct molecules containing bridgehead double bonds that encompass Bredt's rule. For the first time, this topic is reviewed in a natural product context. [ABSTRACT FROM AUTHOR]

Die Bredt ‐ Regel für Brückenkopfalkene ist für physikalisch ‐ organische Chemiker von großem Interesse, wurde jedoch selten auf Naturstoffe angewendet. In der Zuschrift auf S. 10754 ff. zeigen C. M. Williams und E.H. Krenske, wie Berechnungen der Olefinspannungsenergie, eingeführt von Schleyer, die Stabilität komplexer Naturstoffe mit Brückenkopfalkenen vorhersagen. Dies hilft, die Plausibilität der Struktur neu identifizierter Naturstoffe, bei denen eine Brückenkopfalkeneinheit vermutet wird, zu prüfen. [ABSTRACT FROM AUTHOR]

Bredt's rule for bridgehead alkenes is important for physical organic chemists, but has been rarely applied to natural products. In their Communication on page 10608 ff., C. M. Williams and E. H. Krenske show that calculations of the olefin strain energy, first introduced by Schleyer, predict the stability of complex natural products containing bridgehead alkenes. This method can be used to determine the viability of the structures of newly identified natural products proposed to contain a bridgehead alkene. [ABSTRACT FROM AUTHOR]