Camptothecin Corey synthesis

There has recently been another crop of publications devoted to camptothecin synthesis. Corey s synthesis includes a resolution at an early stage, and is the first synthesis of optically active 205-camptothecin (237) (Scheme 33) unfortunately the yield in the vital coupling-cyclization step (xxi—xxii) is very low indeed (6.5%). 

Cyanosilylation of ketones (4,542-543 5,720). In a total synthesis of natural camptothecin (9), Corey et al used this f-butyldimethylsilyl derivative rather than trimethylsilyl cyanide (5, 720-722) to effect cyanosilylation of a ketone (1). Hydrolysis of the resulting cyano silyl ether to the required amide was not accompanied by desilylation with reversal of cyanohydrin formation. By use of carefully controlled conditions and with dicyclohexyl-18-crown-6-potassium cyanide as catalyst, they were able to convert (1) into the a-hydroxy... 

Camptothecin.— The alkaloid camptothecin (3), which exhibits antileukemic and cytostatic activity, has been a vogue target for a number of years, and several syntheses are known. Biichi has now devised a short synthesis of the racemic compound (3) in which the fragment (5) was coupled with the amine (4) to give an intermediate (6). This substance (6) was then cyclized as indicated, and two further steps gave the target, (3). Crouse, under Corey s direction, has described the first... 

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