6β-[2-Methylbutanoyloxy]tropan-3α-ol, a new alkaloid from Datura ceratocaula structure and biosynthesis

Alkaloids of the Genus Datura: Review of a Rich Resource for Natural Product Discovery

“…Welegergs et al [48] purified a trisubstituted tropane alkaloid (β-7) from D. stramonium seeds using a combination of silica gel chromatography and preparative TLC; Siddiqui and co-workers similarly used preparative TLC (chloroform/ether) to isolate the nonpolar benzoyltropane datumetine (8) from D. metel, which they then recrystallized as a high-purity hydrochloride salt [45]. In a unique example of column chromatography, Beresford and Woolley first used a column of Kieselguhr (diatomaceous earth) buffered with phosphate (pH 6.8) to fractionate D. ceratocaula aerial part extract into three "bases" when eluting with light petrol followed by ether; alkaloid 8 (SI Table S1) was isolated from one fraction [49]. A method for isolation of high purity 2 (>99%) from "Hindu Datura" (presumably D. metel) flowers was recently reported by Fu [50].…”

“…As most alkaloids are chiral compounds, polarimetry (the rotation of plane-polarized light) is sometimes used in elucidation of absolute configuration as part of characterization. One elegant example is found in the work of Beresford and Woolley [ 49 ] who isolated alkaloid 9 (above and below) from D. ceratocaula . This alkaloid contains two chiral moieties (the tropane and the methylbutyric acid), which were first separated by hydrolysis of the ester bond.…”

“…To perform structural determination of an alkaloid by NMR, generally 1–5 mg of a compound is required, which often makes isolation (and purification) of enough compound from a natural source a major barrier to NMR experiments. Additionally, as most alkaloids are chiral molecules, a downside of NMR, like mass spectrometry, is the inability of the method to establish absolute stereochemical configuration (e.g., enantiomeric identity or ratio)—that is usually established by chiral HPLC and comparison to a standard, circular dichroism or similar methods, X-ray crystallography, or chemical derivatization (although often not used for Datura alkaloids) [ 47 , 49 , 92 ]. However, in the presence of so-termed chiral shift reagents, enantiomers can be differentiated and quantified by NMR.…”

“…Most short-chain carboxylic acids are derived from amino acids. 2-Methylbutanoyl and tigloyl groups (both very common in Datura tropanes) are synthesized from isoleucine [ 49 , 104 ], whereas isobutyroyl and 3-methylbutanoyl (isovaleroyl) groups are derived from valine and leucine, respectively [ 105 , 106 ].…”

Characterization of Positional and Configurational Tropane Alkaloid Isomers by Combining GC with NPD, MS and FTIR

“…4 (10) 2009Christen et al Indeed, while this isomer possesses a typical base peak at m/z 94 (C 6 H 8 N + ), the three other alkaloids exhibited a prominent signal at m/z 113 (C 6 H 11 NO) (typical base peaks of 3-or 6-substituted tropane nucleus, respectively [15]). Thus, EI mass spectra can easily differentiate between C-3 and C-6 esterified hydroxytropanes [15,16]. As mentioned above, the identification of 2 was further confirmed by injecting separately the pure isolated compound.…”