Unique natural product

Squalene is a unique natural product of a C30H50 structure with 6 non-conjugated double bonds. Hence, its MS shows a fragmentation pattern typical of non-conjugated... 

Table 16.2.5.IV. Endangered unique natural products in Indian Ocean coral reefe...

H. Schmutterer (ed.), The Neem Tree Azadirachta indica A. Juss. and Other Meliaceous Plants Sources of unique natural products for integrated pest management, medicine, industry and other purposes , VCH, Wein-heim, 1995, 696 pp. 

In total synthesis of the structurally unique natural product calcimycin (15), Grieco and others used Ireland-Claisen rearrangement of the ester 17 to synthesize the key intermediate (18)7 (Scheme 1.3g). Monosilylation of the diol 16 followed by treatment with propionyl chloride in pyridine gave rise to the ester 17 in 90% yield. Treatment of 17 with LDA in THF at —78 C, subsequent addition of ferf-butyldimethylsilyl chloride in HMPA, and brief heating of the resulting silylketene acetal provided the corresponding silyl ester. Subsequent hydrolysis of the silyl ester and esterification with diazomethane gave 18 in 90% yield from 17. 

O2, unique natural product revolutionary transformation of biology and chemistry... 

Aside from the well-documented ability of the Luche reduction to provide stereocontrol in cyclic systems, acyclic stereocontrol is also viable through this process.39-41 A notable example of this was demonstrated in the synthesis of (+)-cannabisativine, a unique natural product found in the common marijuana plant.42 This synthesis necessitated a stereoselective Luche reduction to produce the diol 36 as a single diastereomer. The reaction proceeded in 96% yield and with 95% de. The pronounced diastereoselectivity can be attributed to Cram s rule, in which the hydride ion is delivered from the least sterically hindered side of the intermediate 34. Reduction via the chelated intermediate 35 would also account for the observed stereochemical outcome. 

The diazonamides A and B 1192a and 1192b are singularly unique natural products isolated from the colonial ascidian Dizona chinensis. Diazonamide A... 

Tables 1 and 2 provide one example of GC-MS results from analysis of the same urine sample by ECC/CT and SPME, respectively. Clearly, ECC/CT facilitates the observation of the more volatile organic compounds. Tables 3 and 4 illustrate typical results from automated SPME/GC-MS analysis of a urine sample at physiological pH 8 versus pH 3. It is noteworthy that the compounds listed in Table 4 (pH 3) at retention times of 64.49, 65.40, 65.69, 66.24, 66.49, 67.24, and 67.89 minutes constitute a total of 62.48 area percent of the total products observed, while none of these compounds appear at all in the pH 8 sample. The compound at 64.49 minutes is a known synthetic spirocycle (1) that has not been observed previously as a natural product (Ehrenfreund et al., 1974 Renold et al., 1975 Schulte-Elte, et al., 1978). This is not the first time that we have observed unique natural products in African elephant secretions and excretions (Goodwin et al, 1999, 2002).

H Schmutter, The Neem Tree Source of Unique Natural Products For Integrated Pest Management, Medicine, Industry and other Purpose, VCH, Weinheim, Germany, 1995. 

The alkaloidal antibiotic, U-47,929 (also known as ficellomycin, 15), was isolated from Streptomyces ficellus [41]. Interestingly, it inhibited the growth of Gram-positive bacteria in vitro and is effective in the treatment of experimental Staphylococcus aureus infections in mice [42]. Structural elucidation of (15) [43] was eventually achieved by a combination of NMR, mass spectrometry, and formation of derivatives. The l-azabicyclo[3.1.0]hexane moiety in (15) represents an unusual ring system making ficellomycin a unique natural product [43]. 

Castor oil is a unique natural product used in many industries and many types of products. With its 85-90% content of the hydroxy FA ricinoleic acid, castor oil provides this FA at the equivalent of a technical grade of purity, a rare natural phenomenon. The uses of castor oil in industry are limited by the availability of the oil. The presence of a midchain hydroxyl group and the polyol nature of castor oil provide nearly endless possibilities for chemists to develop new applications for the oil. More widespread cultivation of the castor plant will expand utilization of castor oil by industry. 

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