Starting from (−)-quinic acid, the title compound was synthesized in seven chemical steps and an overall yield of 35−38%.
The route of the improved Gilead synthesis was not changed.
However, significant improvements in each step led to a doubled
overall yield, a 30% reduction in the number of unit operations,
and an excellent quality (≥99%) of the resulting epoxide. A
highly regioselective method for the dehydration of a quinic
acid to a shikimic acid derivative and for the reduction of a
cyclic ketal was found. Alternatively, the title compound was
synthesized in six chemical steps and 63−65% yield from
commercially available (−)-shikimic acid. Compared to the
optimized quinic acid route, the production time was reduced
by about 50%. The quality of epoxide produced from either
natural product was equivalent. Therefore (−)-shikimic acid
is the preferred raw material. The absolute configuration of
the epoxide was determined by X-ray single crystal structure
analysis and it was demonstrated that the epoxide was stereoisomerically pure.
SummaryElectrolytic oxidation of 4,5,7,8-tetramethyl[2.2]paracyclophane (I) yields a paramagnetic species which by ESR. spectroscopic evidence must be ascribed to the dimeric radical cation IZ . @. Analogous dimers are obtained from the 12,13,15,16-tetradeuterio-and 1,1,10,10,12,13,15,16-octadeuterio-derivatives of I so that all coupling constants can be unequivocally assigned to sets of equivalent protons. The hyperfine data for IZ . @ are consistent with an effective D2h or D2d symmetry, the four benzene rings lying in parallel planes.
Das aus dem cyclischen Sulfon (I) bei einer Pyrolyse in geringer Menge entstehende Paracyclopyridinophan (II) entsteht auch bei der Mischpyrolyse der beiden quartären Ammoniumbasen (III) und (IV) und kann durch fraktionierte Kristallisation und Säulenchromatographie von den Hauptprodukten (V) und (VI) und den Nebenprodukten (VII)‐(X) abgetrennt werden.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.