dl‐Pumiliotoxin‐C (4) was synthesized in a practical manner from trans‐4‐hexenal (9). The key step 14 → 15 (Scheme 3) involves an intramolecular Diels‐Alder reaction giving mainly the cis‐fused indanols 15a, which were converted to the cis‐fused ketone 16. After Beckmann‐rearrangement of 16 the octahydroquinolinone 7 was transformed to the lactim‐ether 23. (Scheme 7). Reaction of 23 with propylmagnesium bromide followed by hydrogenation furnished dl‐4 in a highly stereoselective fashion.

Die pentacyclische Modellverbindung 10 wurde durch autoxydative Indol-Chinolon-Umlagerung in 12 umgewandelt und dieses iiber einige einfache Reaktionsschritte (4 14-+15) in den aromatischen Grundkbrper 11 des Camptothecins (1) iibergefiihrt. Reactions with Indole Derivatives, XVIThe Autoxidative Indole-quinolone Rearrangement of a Camptothecin Model CompoundThe pentacyclic model compound 10 is transformed into 12 by autoxidative indole-quinolone rearrangement. 12 yields in some simple reaction steps (+ 14 + 15) the aromatic camptothecin analogue 11.Das pentacyclische Alkaloid Camptothecin (l), das von Wall2) aus der Rinde und dem Holz des in Zentralchina heimischen Baumes Camptotheca acuminata (Nyssacee) isoliert worden war, erwies sich als eine der aktivsten natiirlich vorkommenden antiTumor-wirksamen Substanzen3). In Tierversuchen wurde hohe Aktivitat gegen Leu-

~~~~Summary dl-Pumiliotoxin-C (4) was synthesized in a practical manner from trans-4-hexenal (9). The key step 14+15 (Scheme 3) involves an intramolecular Dielv-Alder reaction giving mainly the ciy-fused indanols 15a, which were converted to the cis-fused kctone 16. After Beckmann-rearrangement of 16 the octahydroquinolinone 7 was transfoimed to the lactim-ether 23. (Scheme 7). Reaction of 23 with propylmagnesium bromide followed by hydrogenation furnished dl-4 in a highly stereoselective fashion. . The complex stereochemical features 2, and the paucity of this physiologically active alkaloid provide a considerable challenge to the synthetic chemist [3-61. We have recently met this challenge by using the intramolecular Diels-Alder reaction 2 + 3 as the crucial step in the synthesis outlined below3) (Scheme 1 ) ; one of its key features is that during the conversion of 1 to 4 the original chiral center of the amine 1 controls to a major extent the configuration of the other chiral centers which are formed simultaneously in the cycloaddition process.We now wish to report an alternative synthetic scheme (5 i 6 i 7 --f 4) following a different stereochemical strategy in which center C(2) is induced by the other three chiral centers*) during the transformation 7 i 4; for their assembly an intramolecular cycloaddition 5 + 6 was envisaged. Since both trans-dienes 5a, as well as the corresponding cis-dienes (5b) may be considered as leading selectively to the required cis-junction of 6 the two isomeric trienols 11 and 12 were separately prepared from the dienynol 10 in a stereocontrolled manner.

Die pentacyclische Modellverbindung 10 wurde durch autoxydative Indol-Chinolon-Umlagerung in 12 umgewandelt und dieses iiber einige einfache Reaktionsschritte (4 14-+15) in den aromatischen Grundkbrper 11 des Camptothecins (1) iibergefiihrt. Reactions with Indole Derivatives, XVIThe Autoxidative Indole-quinolone Rearrangement of a Camptothecin Model CompoundThe pentacyclic model compound 10 is transformed into 12 by autoxidative indole-quinolone rearrangement. 12 yields in some simple reaction steps (+ 14 + 15) the aromatic camptothecin analogue 11.Das pentacyclische Alkaloid Camptothecin (l), das von Wall2) aus der Rinde und dem Holz des in Zentralchina heimischen Baumes Camptotheca acuminata (Nyssacee) isoliert worden war, erwies sich als eine der aktivsten natiirlich vorkommenden anti-Tumor-wirksamen Substanzen3). In Tierversuchen wurde hohe Aktivitat gegen Leu-2 1) XV. Mitteil.: E. Winterfeldt, J. M. Nelke und T. Korth, Chem. Ber. 104, 802 (1971).