The crystal structure and absolute configuration of koetjapic acid were unambiguously reassigned by X-ray crystallography with strong support from NMR spectroscopic data. The acid contained 9 quaternary carbon atoms existing as an orthorhombic crystal with a space group of P212121 and unit cell parameters of a = 7.6641(2), b = 14.6844(4) and c = 23.9316(6). Ring A adopted a chair conformation, ring B has an envelope conformation, whilst ring C assumed a halfchair and D displayed a chair conformation. The absolute configurations at C1 (R), C5 (R), C7 (S), C10 (S), C13 (R), C14 (R), C17 (S) and C18 (S) were assigned for the first time. The X-ray crystal of koetjapic acid was therefore reassigned as 3,4-seco-olean-4(23),12-diene-3,30-dioic acid. A plausible biogenetic synthetic pathway for compound 1 is also proposed.
CITATION STYLE
Abubakar, S., Murugaiyah, V., Teh, C. H., & Chan, K. L. (2017). Structural reassignment of koetjapic acid following X-ray crystallography and nmr spectroscopy. Natural Product Communications, 12(7), 1017–1020. https://doi.org/10.1177/1934578x1701200704
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