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3-Amyrin structure

Partial Synthesis of a-Amyrin Acetate Proof of the Structure and Stereochemistry... [Pg.239]

Tenerife and La Palma, revealed the existence of luteolin and an array of simple phenolic derivatives as well as three known phytosterols, B-amyrin, sitosterol, and stigmasterol. The phenols identified comprised a set of phenylpropanoids myristicin [566] (see Fig. 6.16 for structures 566-573), methyleugenol [567], todadiol [568], todatriol [569], crocatone [570], elemicin [571], apiole [572], and the coumarin scopoletin [573]. The occurrence of these compounds is recorded in Table 6.5. The differences between the two profiles were taken by Gonzalez and his co-workers... [Pg.283]

Regert et al. studied [9] a series of 30 Neolithic hafting adhesives from lake dwellings at Chalain (France) using an analytical procedure based on GC/MS analysis involving solvent extraction (dichloromethane) and trimethylsilylation. In the majority of the samples a series of triterpenoid compounds with a lupane structure was clearly identified on the basis of their TMS mass spectra. In particular, the presence of betulin, betulone, lupenone, lupeol and lupa-2,20(29)-dien-28-ol allowed birch bark tar to be identified. In other samples the co-occurrence of other plant biomarkers such as a-amyrin,(3-amyrin... [Pg.222]

The use of HMDS as a derivatization reagent in the analysis of triterpenoid resins has been less explored. The TMS derivatives of triterpenoids bearing hydroxyl groups [a-amyrine, p-amyrine and hop-22(29)-en-3p-ol] have been identified in the triterpenic fraction of Burseraceae resins, thus demonstrating that HMDS combined with Py-GC/MS is effective in the derivatization of triterpenoid compounds [59]. However, the range of structures that can be fully derivatized and detected must be extended and, in order to get comprehensive results comparable with those coming from the well assessed off-line GC/MS procedures, general improvements in the on-line trimethylsilylation-pyrolysis method are needed. [Pg.342]

More than 1500 triterpenoids have been discovered based on 40 skeletal types. Some examples include amyrin (produced by terrestrial plants), cephalosporin (synthesized by marine bacteria), and the steranes. The skeletal structure of the last contains three six-membered carbon rings and one five-membered ring (Figure 22.19a). [Pg.594]

Among the recent outstanding contributions to the chemistry of natural products is the conformational analysis designed by Derek Barton. He used it for the structural determinations of many complex molecules such as P-amyrin and cycloartenol. Robert B. Woodward was involved in the structural determinations of penicillin, strychnine, patalin, terramycin, aureomycin and the synthesis ofVitamin B12. [Pg.4]

Johnson in 1993 described an approach to racemic p-amyrin involving application of a biomimctic polyene cyclization.7 In the same year Corey accomplished the enantioseleetive synthesis of compound 4. a key intermediate that opened the way to stereoselective preparation of compounds I, 2. and 3 8 A key step in the synthesis of P-amyrin (1) was the introduction of chiral oxazaboroli-dines for enantioseleetive carbonyl reduction. Ba ed on these methods, generation of an enantiomerically pure epoxide and its stereoselective cationic cyclization led to the pentacyclic system of structure 1 Diastereoselective cyclopropanation and an intramolecular protonation of a carbanion represent other interesting steps in this total synthesis. [Pg.179]

The pentacyclic triterpenoid skeletons exemplified by lupeol, a-amyrin, and p-amyrin (Figure 5.60) are frequently encountered in the form of triterpenoid saponin structures. Saponins are... [Pg.219]

The structures of two important sterols, the desmethylsterol fi-sitostcrol (I) and the triterpene alcohol a-amyrin (II), are shown in Figure 3.1. [Pg.79]


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See also in sourсe #XX -- [ Pg.488 ]




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