111026-10-9Relevant articles and documents
Carbene Ligands as Anthracyclinone Synthons, 6. - Metal Carbene Chelates as Key Reagents in Syntheses of the Daunomycinone Series: Regiospecific Annulation of Arylcarbene Ligands as a Strategy towards the Synthesis of Rings B and C
Doetz, Karl Heinz,Popall, Michael
, p. 665 - 672 (2007/10/02)
Reaction of tetracarbonyl carbene chelates of chromium 4, 5, and 18 with terminal alkynes leads to regiospecific annulation of the carbene ligands to give key intermediates in anthracyclinone synthesis.The B-ring of daunomycinone is formed by reaction of 3-(methoxycarbonyl)-5-hexynoate 1 with the naphthylcarbene complexes 4/5.The metal is recycled as hexacarbonylchromium by decomplexation of the anthracenol complexes 6/7 under CO pressure.Conventional steps lead to the tetracyclic systems 14/15 which serve as precursors to daunomycinone C and its 4-demethoxy analogue.The synthesis of ring C involves the annulation of the anisyl complex 18 by the propargylcyclohexanediones 16/17, and - after cleavage of the metal - leads to the naphthol derivatives 21/22.The functionalization of the ketone 23 to give the acid 24 via isocyanomethyl p-tolyl sulfone and the cyclization using TFA/TFAA are key steps towards the tetracyclic diketone 25 which is a well-known precursor of 11-deoxydaunomycinone E.
