The 13C NMR spectrum of the pentacyclic triterpene friedelin was fully assigned, taking into account signal multiplicities, correlations of the carbon lines with known proton resonances and Eu‐induced shifts. This work clarifies the situation prevalent in the literature, in which three separate groups have published contradictory information. In addition, the carbon and proton spectra of the naturally occurring 3α‐hydroxyfriedelan‐2‐one and its synthetic acetate were analysed. The different preferred conformations of the D/E rings for friedelin (boat‐boat) and polpunonic acid (chair‐chair) are rationalized.
Bibliographical noteFunding Information:
GM receives research funding from Astellas Inc and SymBio Pharmaceuticals Limited. MH receives research funding from Incyte. AS is the site principal investigator of clinical trials for genome editing of sickle cell disease sponsored by Vertex Pharmaceuticals/CRISPR Therapeutics (clinicaltrials gov. Identifier: NCT03745287) and Novartis (clinicaltrials gov. Identifier: NCT04443907). The industry sponsors provide funding for the clinical trial, which includes salary support paid to AS institution. AS has received consultant fee from Spotlight Therapeutics, Medexus Inc. and Vertex Pharmaceuticals. AS has also received research funding from CRISPR Therapeutics and honoraria from Vindico Medical Education. JH receives research funding from Global Blood Therapeutics and consultancy fees from Global Blood Therapeutics, Forma Therapeutics and bluebird bio. SB receives grant support from the American Society of Hematology.