Isolation and structural characterisation of Kamahine C: An unusual spiroketal found in a native New Zealand honey

The diethyl ether extract of honey from the flowers of the New Zealand native tree Kamahi (Weinmannia racemosa) has been found to contain three diastereoisomers of an unusual degraded carotenoid with a 14 carbon skeleton. After acetylation, one of the isomers, 1b, was fully characterised by multidimensional 1H and 13C NMR spectroscopy and single crystal X-ray crystallography, showing that the parent alcohol (Kamahine C, 1a) was 4,5-dihydro-1′,5-dihydroxy-2′,4,8′,8′-tetramethylspiro[furan-2( 3 ) H,7′-[6]oxabicyclo-[3.2.1]oct[2]ene]-4′-one.