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1978 (1)
1Author    R. Hansel, J. Schulz, A. Pelter, M. T. Ayoub, R. ReinhardtRequires cookie*
 Title    Über das Verhalten von 5-Hydroxy-Kawainen gegen Alkali Behaviour of 5-Hydroxykawain Derivatives under Mild Alkaline Conditions  
 Abstract    Treatment of cis-dihydroxykawainol = rel (5R, 6R)-(±)-5-hydroxy-4-methoxy-6-phenylethyl-5,6-dihydro-2H-pyran-2-on (eis-3) with potassium hydroxide in methanol (2.5%, 1 h, room temp.) leads to a 1:1 mixture of the corresponding erythro-butenolide 7 and threo-butenolide 8 by a ring contraction process that may have analogies with the biosynthesis of the piperolides 15. Trans-3 gives the same yields (about 70%) of the same mixture (7 and S), which can be separated by silica-gel columns. Starting from mixtures of cis-5-hydroxykawain (C?Ö'-4) and Zrans-5-hydroxykawain (trans-4), there were prepared and described the two epimeric dehydro-butenolides 9 and 10 and their O-methyl-derivatives 11 and 12. The threo-and erythro-series show consistant differences between ,75,6 and the X H NMR spectra. The constitution and configuration of (±)-erythro-5-(l-methoxy-3-phenylallyl)-4-methoxy-2(5H)-furanone (11) were established by X-ray analysis. 
  Reference    Z. Naturforsch. 33b, 1020—1025 (1978); eingegangen am 5. Juni 1978 
  Published    1978 
  Keywords    5-Hydroxykawain Derivatives, Erythrobutenolides, Threobutenolides, X-ray, Piperolides 
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 TEI-XML for    default:Reihe_B/33/ZNB-1978-33b-1020.pdf 
 Identifier    ZNB-1978-33b-1020 
 Volume    33