Enantioselective synthesis of a taxol C ring

Abstract

International audienceAn enantioselective synthesis of a C ring of taxol has been accomplished. The key step is an oxidative cleavage of a derivative of the Wieland-Miescher ketone. A first attempt of a Shapiro reaction modelling the coupling of the C ring with the A fragment of taxol was also successful. © 2011 Institute of Organic Chemistry and Biochemistry

Bamford‐Stevens and Shapiro Reactions in Organic Synthesis

“…[49] The same group has published model studies for coupling of A ring and C ring fragments through Shapiro reaction. [50] It should be noted that the coupling role in this case was reversed as compared to Nicolaou's approach. [30] Hydrazone 148 was prepared from Wieland-Miescher ketone in seven steps (scheme 30).…”

“…While investigating cascade ring‐closing metathesis reaction, Prunet group reported a synthesis of an advanced intermediate of taxol [49] . The same group has published model studies for coupling of A ring and C ring fragments through Shapiro reaction [50] . It should be noted that the…”

Study of Cascade Ring-Closing Metathesis Reactions en Route to an Advanced Intermediate of Taxol

“…This cascade metathesis reaction was validated in our previous work on the synthesis of a 7-deoxy ABC tricycle of Taxol as well as Granja et al’s work on the construction of simplified Taxol analogues. , The key step for the assembly of metathesis precursors is a Shapiro coupling reaction between aldehyde 8 and trisylhydrazone 9 . This reaction was shown to be incompatible with the presence of an olefin at C10 in the hydrazone C ring, so the olefin at C10 and the alcohol at C7 were masked as a methyl ketal in compound 9 …”

“…3, 56.5, 48.7, 36.5, 29.3, 27.3, 26.0, 20.9, 16.3. IR (ν, cm −1 ): 2854,2747,2641,1736,1431,1337,1264,1247,1080,984,953 2,4,6-Triisopropyl-N′-((2S,4S,8S)-2-methoxy-4-methyloctahydro-5H-chromen-5-ylidene)benzenesulfonohydrazide (9). To a solution of acetal 14 (14.5 g, 73.2 mmol) in THF (100 mL) were added TrisNHNH 2 (23.8 g, 80.5 mmol, 1.1 equiv) and concentrated HCl (4 drops).…”