Photochemical reactions contribute in a significant way to the existing repertoire of carbon-carbon bond-forming reactions by allowing access to exceptional molecular structures that cannot be obtained by conventional means. In this Review, the most important photochemical transformations that have been employed in natural product synthesis are presented. Selected total syntheses are discussed as examples, with particular attention given to the photochemical key step and its stereoselectivity. The structural relationship between the photochemically generated molecule and the natural product is shown, and, where necessary, the consecutive reactions in the synthesis are illustrated and classified.

Photochemical reactions as key steps in natural product synthesis

Photochemische Reaktionen bereichern in signifikanter Weise das Repertoire zur Knupfung von Kohlenstoff-Kohlenstoff-Bindungen und machen ungewohnliche, auf herkommlichem Weg nicht erhaltliche Molekulgeruste zuganglich. In diesem Aufsatz werden die wichtigsten Umsetzungen der Photochemie vorgestellt, die auf breiter Front Einzug in die Naturstoffsynthese gehalten haben. Beispielhaft werden einzelne Totalsynthesen diskutiert, wobei besonderes Augenmerk auf den photochemischen Schlusselschritt sowie dessen Stereoselektivitat gerichtet ist. Dabei wird das photochemisch erzeugte Molekul in Relation zur Struktur des Naturstoffs gebracht, und Folgereaktionen werden, wo notwendig, illustriert und klassifiziert.

Photochemische Reaktionen als Schlüsselschritte in der Naturstoffsynthese

Protection for the Hydroxyl Group, Including 1,2‐ and 1,3‐Diols

The intramolecular [2 + 2] photoaddition/cyclobutane-fragmentation sequence in organic synthesis

The synthesis of novel dendrimers functionalized with laser dyes both at the periphery and at the core, along with all relevant model compounds necessary for accurate photophysical studies, is described. The utilized synthetic strategy involves a modular approach in which a variety of peripheral and core moieties can be placed on a dendritic structure bearing electrophilic peripheral groups and a nucleophilic core. Specifically, the target macromolecules required functionalization with the laser dyes coumarin 2 (periphery) and coumarin 343 (core) due to the possibility of energy transfer from the former to the latter dye. In addition, the preparation of a novel, highly soluble and reactive hypermonomer utilized in the rapid and efficient synthesis of high-generation dye-labeled dendrimers and model compounds is outlined.

Marc Demuynck

Papers

(.+-.)-Hysterin: revised structure and total synthesis