The cleavage of alkenes to the corresponding carbonyl products is a widely employed method in organic synthesis, especially to introduce oxygen functionalities into molecules, remove protecting groups and tailor large molecules. Chemical methods available for alkene cleavage include, for instance, ozonolysis, several metal-based variants (KMnO 4 , OsO 4 , RuO 4 , etc.), electrochemical alternatives, singlet oxygen, hypervalent iodine and organic molecules in combination with oxygen. Furthermore, several enzymatic methods for alkene cleavage have been described to establish safe, mild and selective oxidation methods. Various heme and non-heme iron-dependent enzymes catalyse the alkene cleavage at ambient temperature and atmospheric pressure in an aqueous buffer, showing good chemo-and regioselectivities in selected cases. Quite recently some Cu-, Mn-and Ni-dependent enzymes have been identified for this reaction. This review gives an overview of the different chemical and enzymatic methods available for the cleavage of alkenes.

The first syntheses are reported for recently isolated drimanes 11,12-epoxydrim-8,12-en-11-ol (2) and 11,12-diacetoxydrimane (3), from (-)-sclareol (1). Furthermore, two efficient new routes to the potent bioactive warburganal (4) starting also from 1 are described.

An enzyme preparation of Trametes hirsuta cleaves alkenes following neither the classical dioxygenase mechanism nor via a monooxygenase mechanism. A catalytic cycle for an alternative enzymatic alkene cleavage was proposed, whereby two oxygen atoms derived from two different oxygen molecules are incorporated into the product(s).

No abstract