Pathways D and

5N HCl resultated in the formation of adamantane-diol 13 as sole product, i.e. in 

20 both epoxides were cleaved only by trans-opening of the oxygen-carbon bonds to C(3) and C(7), resp. However, analogous treatment of the exo,exo-2,3-endo,endo- 

7- diepoxide (anti) 27 yielded not only 13 but also 4° l0 -dihydroxy- 

7- dioxa-isotwistane (22) . The endo-epoxide ring in 27 was therefore opened in two ways cleavage of the bond O—C(6) - endo-OH at C(7) and cleavage of the bond 

0—C(7) - endo-OH at C(6), each by trans-opening of the epoxide ring. Both diols 13 and 22 were also characterized as their diacetates 9 and 23.  

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Fig. 13. Schematic model for electron injection of RuN3. Following MLCT excitation of the RuN3-sensitized Ti02 nanocrystalline film, electron injection occurs from both excited states of the dye, MLCT and MLCT, into the conduction band (CB) of the semiconductor. GS ground state of RuN3. Pathway A electron injection from the initially excited delocalized MLCT excited state. Pathway A2 ISC and localization in the MLCT excited state. Pathway B electron injection from the hot MLCT excited state of the attached bipyridine ligand (not observed in the present study). Pathway C internal vibrational relaxation in the MLCT excited state of the non-attached bipyridine ligand. Pathways D and E ILET between the bipyridine ligands and ensuing electron injection.

The aUcyl radicals formed by the abstraction reaction react exclusively with O2 in the atmosphere to form alkylperoxy radicals (pathways (c) (h)), and most of them are then transformed to alkoxy radicals by oxidizing NO to NO2 in the presence of NOx (pathways (d) and (i)). However, some alkylperoxy radicals react with NO by the recombination isomerization reactions (e) and (j), to form alkyl nitrate (see Sect. 5.3.3). Although the yields of 2-butyl and 1-butyl nitrate are not large in the case of 2-butyl and 1-butyl radicals, 0.083 and <0.04, respectively, the production yields of alkyl nitrates increase with the increase of carbon number of alkyl radicals as described in Sect. 5.3.3, and it is as large as >0.2 for the Cg, and C7 secondary n-aUcyl radicals (2-hexyl, 3-hexyl, 2-heptyl, and 3-heptyl radicals) (Lightfoot et al. 1992 Arey et al. 2001). Since these reactions act as termination reactions for the OH chain reaction, they are important as parameters in determining the ozone formation efficiency in model calculations. The production yields of RONO2... 

Reaction Scheme 7.2 summarizes the reaction mechanism for 1-butene (l-C4Hg) as an example of alkenes. The hydroxyalkyl radicals formed by the pathways (a) and (b) is a kind of alkyl radicals mentioned in the previous Sect. (7.2.2), and exclusively forms hydroxyperoxy radicals by the reaction with O2 in the atmosphere. From the hydroxyperoxy radicals, oxyradicals (hydroxybutoxy radicals) and NO2 (pathways (d), (k)), and partially hydroxybutyl nitrate (pathways (e), (1)) are produced by the reaction with NO as in the case of alkylperoxy radicals described in the previous paragraph. The yields of hydroxylalkyl nitrates are 2-6 % for C4-C6 alkenes (O Brien et al. 1998), which is about half of those for alkyl nitrates from the alkoxy radicals. Hydroxy alkoxy radicals formed in pathways (d) and (k) are known to follow the three reaction pathways, unimolecular decomposition ((g), (n)), H-atom abstraction by O2 ((h), (o)), and dihydroxyl radical formation by isomerization (p), corresponding to reactions (7.25), (7.24) and... 

Bryngelson J D, Onuchic J N, Socci N D and Wolynes P G 1995 Funnels, pathways, and the energy landscape of protein folding a synthesis Profe/ns 21 167-95... 

This enzyme interconverts ribulose-5-P and ribose-5-P via an enediol intermediate (Figure 23.30). The reaction (and mechanism) is quite similar to the phosphoglucoisomerase reaction of glycolysis, which interconverts glucose-6-P and fructose-6-P. The ribose-5-P produced in this reaction is utilized in the biosynthesis of coenzymes (including N/ DH, N/ DPH, F/ D, and Big), nucleotides, and nucleic acids (DNA and RNA). The net reaction for the first four steps of the pentose phosphate pathway is... 

Thomas, C. E. Kuhn, I. F. James, B. D. Lomax, F. D. and Baum, G. N. (1998). Affordable Hydrogen Supply Pathways for Fuel Cell Vehicles. InternnaomilJournal of Ilydrogcn Energy 23(6). 

Whereas the reactions of sulfones with nucleophiles via pathways A and B of equation 1 are most frequently observed, the nucleophilic substitution reaction by pathway D has been observed only in the cases where the leaving carbanion can be stabilized, or in the highly strained molecules. Chou and Chang3 has found recently that an organolithium reagent attacks the sulfur atom of the strained four-membered sulfone in 34. When this sulfone is treated with 1 equivalent methyllithium, followed by workup with water or Mel, 38 or 39 are formed in high yield. 

Most of the acetyl-CoA formed by 3-oxidation in liver is converted to acetoacetate by the 3-hydroxy-3-methylglutaryl-CoA pathway (Guzman and Gelen, 1993). Acetoacetate is reversibly converted to D-3-hydroxybutyrate by D-3-hy-droxybutyrate dehydrogenase in the mitochondrial matrix in all tissues. 

During the second part of the experiment the examined compounds were applied repeatedly both to mice and rats. The same parameters, as after single administration were estimated in the serum and liver. Additionally, ALA-D and ALA-S, the two enzymes from haeme biosynthesis pathway were evaluated in the liver. 

The results obtained after 7-fold administration of all studied compounds, suggest that these compounds cause disturbances in the heame biosynthesis pathway changes in the activities of ALA-D and ALA-S were observed. Such results suggest the possibility of liver impairment of porphyrogenic type as a result of multiple administration of brominated compounds. 

Figure 24-2. Biosynthesis of triaq/lglycerol and phospholipids. ( , Monoacylglycerol pathway (D, glycerol phosphate pathway.) Phosphatidylethanolamine may be formed from ethanolamine by a pathway similar to that shown for the formation of phosphatidylcholine from choline.

Figure 6.7. Hypothetical representation of a set of architectural domains defined by monomer concentration and proportion of lipid. Each defines structure regardless of the exact composition, providing this lies within its boundary. Letters a to d and a to d represent specific concentrations of components. The dotted line d to d shows a pathway of changing concentration by which a spore wall such as that shown in Figure 6.1(c) might be constructed.

In summary, pathways A, B, and D are the only pathways at room temperature that contribute to products. Pathways A and D both lead to the main product channel (H + CO + CO2), and are isotopicaUy distinguishable, whereas pathway B leads to a different product channel, but must be included in the analysis because it affects the isotope ratios. The observed spectra from the labeled reaction contain only C 0 and OC 0. Therefore, only upper limits can be placed on the isotope ratios. The three values needed to constrain the three pathways under consideration are the ratio limits [C 0]/[C 0] < 0.16 and [ 0C 0]/[ 0C 0] < 0.30, and the limit that the total OH + CO + CO production is <0.10 [45]. 

Proteins B, D and P also amplify the effects ofthe classical pathway in that some of the 3b generated by this pathway interacts with these proteins to form additional C3 convertase that supplements that provided by C4b.2a. Likewise, enhanced cleavage of C5 occurs due to the dual activity of C4.2a.3b and C3b.Bb.C3b complexes. 

It is pertinent, then, to seek a dependence of substitution rates on (/) leaving group, (ii) solvent, Hi) steric crowding, iv) charge, v) nature of non-labile substituents including stereochemistry, consistent with this picture of the activation mode. If these tests generally support d modes it will be desirable to examine rate laws closely to attempt a distinction between D and 7j stoichiometric pathways. 

RONEN G, CARMEL-GOREN L, ZAMIR D and HIRSCHBERG J (2000) An alternative pathway to 13-carotene formation in plant chromoplast discovered by map-based cloning of beta and old-gold color mutations in tomato , Proc Natl Acad Sci, 97, 11102-7. 

Schmidt-Dannert, C., Umeno, D., and Arnold, R, Molecular breeding of carotenoid biosynthetic pathways, Nat. Biotechnol. 18, 750, 2000. 

Pathway A shows the most common reaction where the nucleophilic substitution reaction occurs at the electron-deficient carbon atom due to the strong electron-attracting character of the sulfonyl group. Nucleophilic displacements at the allylic position (Sn2 reaction) are shown in pathway B. Pathway C is the formation of a-sulfonyl carbanion by nucleophilic attack on the carbon atom P to the sulfone moiety. There are relatively few reports on substitution reactions where nucleophiles attack the sulfone functionality and displace a carbanion as illustrated in pathway D. ... 

Pieper D. and Newman S. (1999). Neural pathway from the olfactory bulbs regulating tonic gonadotropin secretion. Neurosci Bio Behav Revs 23, 555-562. 

Soskic, V., Gorlach, M., Poznanovic, S., Boehmer, F. D., and Godovac-Zimmermann, J. (1999). Functional proteomics analysis of signal transduction pathways of the platelet-derived growth factor b receptor. Biochemistry 38, 1757-1764. 

Walter, M. H., D. S. Flo et al. (2007). Apocarotenoid biosynthesis in arbuscular mycorrhizal roots Contributions from methylerythritol phosphate pathway isogenes and tools for its manipulation. 

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