Der Übersichtsartikel (20 Literaturhinweise), vorgetragen auf dem Symposium über "Rhodium in der homogenen Katalyse" in Vszprem, Ungarn, 1978, behandelt die Modifizierung des Katalysatorsystems (I) während der Hydroformylierung von Propylen bei gleichzeitiger Abnahme der katalytischen Aktivität. Die Anwesenheit von Schwefelverbindungen (Schwefelwasserstoff, Kohlenoxysulfid) liefert schwefelhaltige Rhodiumkomplexe, die Anwesenheit von Sauerstoff im Kohlenmonoxid‐WasserstoffaGemisch führt zu Triphenylphosphinoxid.

Earlier we reported on the synthesis of α,4-dicarboxy-2-nitrobenyzl caged compounds (Schaper, K. et al. [2002] Eur. J. Org. Chem., 1037-1046). These compounds have the advantage of an increased hydrophilicity compared with the well-established α-carboxy-2-nitrobenzyl caged compounds; however, the release of the active compound becomes slower due to the introduction of the additional carboxy group. Based upon theoretical calculations we predicted that the release would become faster when the additional carboxy group is moved to the 5-position. Here we describe the synthesis and the photochemical and biological characterization of an α,5-dicarboxy-2-nitrobenyzl caged compound. The high hydrophilicity of the new caging group is maintained due to the fact that the additional carboxy moiety is preserved, while the release of the active species from the new derivative is even faster than for the reference, an α-CNB caged compound.

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