Degradation derivatives

As pheophytin a and pheophytin b are the major degradation derivatives formed during extraction, food processing, and storage, some authors reconunend converting chlorophylls into the more stable pheophytins by treatment with HCl, ion exchange resin, or oxalic acid to estimate the chlorophyll contents. ... 

In the later work, low optical activity (<30% ee) was observed for the products [e.g. 5] and the high asymmetric induction of the earlier work was attributed to carry over of the catalyst or chiral degradation derivatives (oxiranes) of the catalysts. Although the reported stereoselective reduction of acetophenone has been discredited, it has been suggested that the use of a chiral solvent, such as menthyl methyl ether, enhances the asymmetric reduction [7], The veracity of this claim has not been proven. 

Environmental contamination usually consists of a mixture of pollutants and their partially degraded derivatives. Such an ill-defined chemical mixture will eventually lead to the formation of an ecosystem of microbes. The individual member species cannot survive in the toxic and hostile environment. Effective bioremediation technologies should therefore invoke a mixture of microorganisms forming synergistic consortia. Any realistic bioremediation concept is based on the recognition that it is the concerted action of various species, which may bring about the desired clean-up effect. 

The absolute stereochemistry of the C-12 and C-13 oxirane moiety of laureoxolane (157), a colorless unstable bromoether obtained from extracts of Laurencia nipponica, was determined on the basis of a chiral synthesis of 156, a degradative derivative of 157. The C-5 to C-8 unit with two asymmetric centers at C-6 and C-7 of 157 corresponds to (25, 35)-l-benzyloxy-3,4-epoxy-2-butanol (142). Elongation of 142 using butyllithium and copper cyanide followed by the creation of a new epoxide provides 152. Lithium acetylide ethylenediamine complex addition to 152 and subsequent ketalization affords the acetylenic acetonide 153, which is coupled with (2i ,35)-l,2-epoxy-3-benzoyloxypentane (154) to furnish 155. Subsequent five-step transformation of 155 provides 156 [60] (Scheme 37). 

Table 2-2. Structure of amino acid degradation/derivative products found in human hair. ...

About 200 naturally abundant tetraterpenes are known to date and referred to as carotenoids because all of them represent structural variants or degradation derivatives of p-carotene from the carrot Daucus carota (Umbelliferae) with 11 to 12 conjugated CC double bonds. The generally accepted parent name is "carotene" two Greek letters (p, y, s, 9, k, % and /) define all seven of the known end groups. 

The structures of several nonsteroidal degradation products from the action of Nocardia restrtctus on A -3-ketosteroids, and insists into the mechanism of degradation derived therefrom also J. Am. Chem. Soc. 87, 1386 (1965). 

The polyphenolic binaphthyl gossypol 94 displays interesting pharmacological applications like male oral contraceptive, treatment of bronchitis, total inhibitor of HIV 1, and in vitro antiviral activity against herpes type 2 virus and influenza virus (Scheme 26.28). Apogossypol 95, a degradation derivative of gossypol that lacks the aldehyde functions, still has the potent pan-active inhibitor activity of antiapoptotic Bcl-2 family proteins. The naphthoic acid precursor can be obtained by... 

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