Species Successfully Transformed

Major limitation Only a few crop species successfully transformed many are infertile Variability and low level of protein expression... 

A bromoallene was demonstrated to act as an allyl dication equivalent. When treated with Pd(0) in an alcoholic solvent, an ei-hydroxybromoallene provides a mediumsized heterocycle (Scheme 16.101) [106]. The oxidative addition of a bromoallene to Pd(0) generates an allenylpalladium species, which is successively transformed into a Jt-allylpalladium complex through the attack of the hydroxyl group on the sp carbon followed by the protonation of the resulting Pd-carbene complex. Finally, the products are provided as a mixture of regioisomers by the nucleophilic attack of the external methanol. 

TNT is most commonly biotransformed by reduction of the nitro groups. By the sequential addition of two electrons, a nitro group is reduced to a nitroso, a hydroxylamino, and hnally to an amino group. Through successive reductions of the three nitro groups, many bacterial species sequentially transform TNT to aminodi-nitrotoluene, diaminonitrotoluene, and finally triaminotoluene (TAT). However, in some bacterial cultures hydroxylamino-substituted compounds persist without the production of amino-substituted compounds. Two monoamino isomers, 2-amino-4,... 

Complete homogenization and isotope exchange must be achieved, requiring successive transformation of the active traces as well as of the inactive analyte to all chemical species that are considered to occur in the complete system. 

Scheme 4-7. Branched routes of successive transformations resulting in cage-like complexes [Co(L872)] + to [Co(L875)] - formation of intermediate species (A) and (B).

The conversion of boronic acids into phenols has been achieved using visible light catalysis (Scheme 2.32) [42]. hi addition to light, the catalyst components consisted of a ruthenium bipyridine species, an amine, and DMF. All the components were needed for a successful reaction since low conversions were observed if any of the components were absent. The ability to use air as the oxidant was one of the practical aspects of this chemistry. While a wide range of arylboronic acids were successfully transformed into phenols, a pinacol-derived arylboronate also served as a substrate in these reactions (up to 94% conversion). In addition to the ruthenium-catalyzed reaction, a metal-free version of die chemistry was also developed using an organic dye. 

PHEMA 30 in quantitative transformation (Scheme 16(b)). Polymer-end dimehylstibanyl group in PNIPAM 31 was also successfully transformed to the corresponding anionic species by tBu4ZnLi2 in DMF without protection of the amide protons. Subsequent addition of benzoyl chloride (S.Oequiv) gave the desired product 32 with quantitative incorporation of the benzoyl group (Scheme 16(c)). 

Some other unusual carotenoids have been characterized in various species of crustaceans but all appear to be produced by the biotransformation of P-carotene by the crustacean. These successive transformations are summarized in Figure 24.1 and additional information is available... 

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