Phenolic natural products isolated

Figure 2, Phenolic natural products isolated from Salvia miltiorrhiza.

Thus, a synthetic source of promising allelochemicals is essential if we are to comprehensively study the agent s mode of activity and establish its basic structure-activity profile. The proposed work addresses this need. We will synthesize alleopathic natural products isolated from the sunflower (the heliannuols), and structurally related compounds, in optically pure form based on biomimetic phenol-epoxide cyclizations. The bioactivity of the targets and intermediates will be evaluated through laboratory tests on plant germination and growth. Bioassays will be performed on the synthetic intermediates to allow for the development of a preliminary structure-activity profile for these novel natural herbicides. 

Solanaceae), acts as competitive inhibitor for ubiquinone in Complex I. Methyl capsaicin is more potent than capsaicin, indicating that the phenolic OH is not essential for the activity [297]. Other natural inhibitors of Complex I are annonaceous acetogenins. These compounds belong to a wide group of natural products isolated from several species of the Annonaceae family, which include more than 250 molecules with diverse chemical structures. Among the various classes, it seems that monotetrahydrofuranic derivatives are less potent than other acetogenins [296, 299]. 

Nishibe, S., H. Tsukamoto, I. Agata, S. Hisada, K. Shima, and T. Takemoto. Isolation of phenolic compounds from stems of Olea europaea. Shokugaku Zasshil981 35 251-254. Tsukamoto, H., S. Hisada, and S. Nishibe. Studies on the lignans from Oleaceae plants. Proc 26th Symposium on the Chemistry of Natural Products, Kyoto, Japan 1983 26 181—188. Paganuzzi, V. Use of silver nitrate TLC in the analysis of olive oil triterpene alcohols. I. Oils obtained from various anatomical parts of the olives. Riv Ital Sostanze Grasse 1981 58(8) 285-393. 

Phenol is produced through both natural and anthropogenic processes. It is naturally occurring in some foods, human and animal wastes, and decomposing organic material, and is produced endogenously in the gut from the metabolism of aromatic amino acids. Phenol has been isolated from coal tar, but it is now synthetically manufactured (EPA, 2002). Currently, the largest use of phenol is as an intermediate in the production of phenolic resins, which are used in the plywood, adhesive, construction, automotive, and appliance industries. Phenol is also used in the production of synthetic fibers such as nylon and for epoxy resin precursors such as bisphenol-A. 

Very simple sulfones have also been isolated from marine organisms. The isolation of sulfolane (290) from the sponge/tunicate composite Batzella spJLissoclinum sp. was the first report, either terrestrial or marine, of this compound as a natural product [213]. The pyrogallol Phenol B (291), obtained from the red alga Grateloupia filicina, was... 

The key structure of antimicrobial marine natural product, araplysillin-I (28), which was isolated from Psammaplysilla arabica, was synthesized by spiro-annulation of o-phenolic oxime-amide (147) with PIDA [104] (Scheme 18). 

Thalfinine (50), first isolated from Thalictrumfoetidum L., has been obtained from T. minus Race B, and its CD spectrum has been determined. Cleavage (Na/NH3) gave (S)-D-methylarmepavine (52), representing the left-hand portion of the molecule, as the major nonphenolic product, but a phenolic product was not isolated. Because of the co-occurrence of thalirabine (Section II,C, 123) in T. minus Race B, the (S,S) configuration is suspected (52) additionally, the CD curves of thalfinine and epithalfinine (51, not a natural product) are similar to those of thalmirabine and O-methylthalmirabine (55) (see Section II,C, 132). 

These chromenes were further converted into the natural products Neorautane (37%) and Neorautanin (51%), upon Heck reaction with the appropriate phenol derivative in the presence of IiCl and PdCl2 in dry acetone. The 7,15-melhano-15H-dibcnzo[d,g][l,3]dioxocins were isolated as undesired side compounds (R = OMe, 15% R = H, 26%). 

A number of plant natural products have been isolated that inhibit an aspartic protease secreted by Candida albicans [35, 36], the most potent of which (IC50 values 8-14 pM) are the phenolics ellagic acid [35] and mattucinol-7-0-[4",6"-0-(5)-hexahydroxydiphenoyl]-P-glucopyranoside [35] and the triterpene betulinic acid [36] (Table 1). A macromolecule from Anchusa is a potent inhibitor of pepsin (K 20 nM) [37] (Table 1). 

Often used in concert with mass spectrometry, NMR spectroscopy remains an invaluable structural diagnostic tool of particular importance to tricyclic natural products chemistry. For example, the tricyclic phenolic compound moracin P (3) was one of eight previously known compounds identified together with two new isoprenoid-substituted flavanones in isolates of the root bark of mulberry trees <89H(29)807>. In a series of studies of 6-7-5 tricyclic natural products, ID and 2D H and l3C NMR spectroscopy were employed extensively in the structure determination of sesquiterpene lactones (4)—(8) found among the aerial natural products of toxic plants (85P1378,90P551, 90P3875). 

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