Evidence is presented which supports the postulate that the photobilirubins IIA and IIB are diastereoisomers in which the C-3 vinyl group has cyclized intramolecularly. The evidence comes principally from proton n.m.r. spectroscopy at 400 MHz and from chemical considerations. The cyclic structures require the E-configuration at the C-4 double bond in the precursor; this is the first structural evidence for the Z leads to E isomerization in bilirubin and supports the view that the precursor (photobilirubin IA or IB) is (4E, 15Z)-bilirubin. Brief irradiation of photobilirubin II gives bilirubin, a new compound (photobilirubin III) and unchanged starting material. The various photoisomers are discussed in terms of their inter-relationships and biological fates.
Research Article|January 01 1982
Concerning the structure of photobilirubin II
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Biochem J (1982) 201 (1): 179-188.
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M S Stoll, N Vicker, C H Gray, R Bonnett; Concerning the structure of photobilirubin II. Biochem J 1 January 1982; 201 (1): 179–188. doi: https://doi.org/10.1042/bj2010179
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