L-DOPS

Azo-bridged ferrocene oligomers also show a marked dependence on the redox potentials and IT-band characteristics of the solvent, as is usual for class II mixed valence complexes 21,22). As for the conjugated ferrocene dimers, 2 and 241 the effects of solvents on the electron-exchange rates were analyzed on the basis of the Marcus-Hush theory, in which the t/max of the IT band depends on (l/Dop — 1 /Ds), where Dop and Ds are the solvent s optical and static dielectric constants, respectively (155-157). However, a detailed analysis of the solvent effect on z/max of the IT band of the azo-bridged ferrocene oligomers, 252,64+, and 642+, indicates that the i/max shift is dependent not only on the parameters in the Marcus-Hush theory but also on the nature of the solvent as donor or acceptor (92). 

SCHEME 70. Stereoselective synthesis of l-DOPS by BINAP-Ru-catalyzed hydrogenation. 

Asymmetric hydrogenation of racemic 2-substituted (3-keto esters to produce 2-substituted (3-hydroxy esters with two new chiral centers is a powerful method, and it is useful in the production of other pharmaceutical intermediates. The methodology can be used in the preparation of protected threonine derivatives 34, where 34d and 34e are key intermediates for the anti-Parkinsonian agent, L-Dops (35). 

In asymmetric complexes of the type [(bpy)2RuCl(pi-pyz)Ru-(NH3)4L]4+, studies (94) revealed that there is a solvent donor-number (DN)-dependent contribution to the Frank-Condon barrier of approximately 0.006 eV/DN, which completely overwhelms the dielectric-continuum-theory-derived (l/Dop-l/Ds) solvent dependence typically observed in symmetrical dimers. In this case, variations in MMCT Eop with solvent give linear correlations when plotted against solvent dependent AEm, the difference in potential between the two ruthenium(III/II) couples, as shown in Fig. 10. The microscopic origin of this solvent effect was described by Curtis, Sullivan, and Meyer (122) in their study of solvatochromism in the charge transfer transitions of mononuclear Ru(II) and Ru(III) ammine complexes. The dependence... 

From Eq. (19), Egp should be linearly proportional to the solvent term (l/Dop 1/Ils)- This relationship has been demonstrated for weakly coupled mixed valence complexes (see Section (II.C.2.c) and this gives qualitative support to the Hush model. 

Kalinin S, Polak PE, Lin SX, Sakharkar AJ, Pandey SC, Feinstein DL (2011) The noradrenaline precursor L-DOPS reduces pathology in a mouse model of Alzheimer s disease. Neurobiol Aging 33 1651-1663... 

Droxidopa. threo-, 3-Diltydroxy-l.-tvrositte i-threo-3-(3,4-dihydroxyphenyl)serine ( — )-(2, 3R)-2-aimnO-3-hydroxy-3-(3,4-dihydroxy phenyl)propionic acid threo-dopaserine L-iJirw-DOPS l-DOPS SM-5688 Dops. C,HnNO. mol wt 2 3. 9. C 50.71%, H 5.20%, N 6.57%, O 37 52%. Synthetic amino acid precursor of norepinephrine, q.v. Prepn of racemate K. W. Rosenmund, H. Dornsaft,... 

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