Enantioselective syntheses of monotetrahydrofuran Annonaceous acetogenins tonkinecin and annonacin starting from carbohydrates.
The total synthesis of two mono-THF acetogenins, tonkinecin (1) and annonacin (2), is reported in full detail. Terminal acetylene 3 prepared from D-glucono-delta-lactone and asymmetric dihydroxylation was employed as a common intermediate for both targets 1 and 2. Pd(0)-catalyzed coupling reaction of 3 with vinyl iodides 4 and 5, the chiral centers of which were taken from D-xylose and S-(-)-ethyl lactate, afforded enyne 26 and 27, respectively. Selective hydrogenation of 26 or 27 with diimide followed by removal of MOM ethers completed the synthesis of 1. A coupling reaction between the lithium derivative of 3 and epoxide 6 in the presence of boron trifluoride etherate gave 42. Both chiral centers in epoxide 6 were taken from L-ascorbic acid. Subsequent catalytic hydrogenation and MOM protection led to 43b. Introduction of the butenolide moiety by aldol condensation of protected S-lactal followed by cleavage of all MOM ethers completed the synthesis of 2.
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State Key Laboratory of Bio-organic & Natural Products Chemistry and Shanghai-Hong Kong Joint Laboratory in Chemical Synthesis, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 354 Fenglin Road, Shanghai 200032, China.
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D002241:Carbohydrates / Q000737:chemistry*; D005663:Furans / Q000138:chemical synthesis* / Q000737:chemistry; D007783:Lactones / Q000138:chemical synthesis* / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D019684:Magnoliopsida / Q000737:chemistry*; D013058:Mass Spectrometry / Q000379:methods; D013237:Stereoisomerism
D002241:Carbohydrates; D005663:Furans; D007783:Lactones; C100859:tonkinecin; C053442:annonacin