- A Versatile Stereoselective Synthesis of endo,exo-Furofuranones: Application to the Enantioselective Synthesis of Furofuran Lignans
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A new stereoselective route to endo,exo-2,6-diarylfurofuranones has been developed using Mn(III)-mediated intramolecular cyclopropanation and C-H insertion reactions as key C-C bond-forming steps. Mn(III)-mediated oxidative cyclization of acetoacetate derivative 11 afforded 1-acetyl-4-aryl-3-oxabicyclo[3.1.0]hexan-2-one (12) with excellent diastereocontrol (d.r. 22:1). Subsequent Lewis acid-catalyzed opening of the activated cyclopropane ring present in 12 with benzylic alcohols then gave α-acetyl-γ-butyrolactones 16 and 18-20, which reacted efficiently with in situ-generated TfN3 to secure the key α-diazo-γ -butyrolactones 22-25. Highly stereoselective rhodium-catalyzed C-H insertion reactions of diazolactones 22-25 completed the synthesis of endo,exo-2,6-diarylfurofuranones 26-29 in overall yields ranging from 41 to 48% from 1-phenylallyl alcohol (±)-10. The approach developed for the furofuranones 26-29 was then applied to the asymmetric syntheses of four furofuran lignans, (+)-xanthoxylol (1), (+)-methylxanthoxylol (2), (+)-epipinoresinol (3), and (+)-epieudesmin (4), starting from enantiomerically enriched 1-arylallyl alcohol (S)-31.
- Swain, Nigel A.,Brown, Richard C. D.,Bruton, Gordon
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p. 122 - 129
(2007/10/03)
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- A New Synthetic Route to Furofuranoid Lignans via Intramolecular Mukaiyama reaction
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The sequence set out in Scheme 1 provides a short and expedient synthesis of a number of (+/-)-furofuranoid lignans, including styraxin 3 (antitumor), aptosimon 5, asarinin 6, pluviatilol 7, 'MEL' 4 (inhibitor of germination) and related compounds.
- Stevens, David R.,Till, Clive P.,Whiting, Donald A.
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p. 185 - 190
(2007/10/02)
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