2V-Acetylation

Das Hydroxyl am C-Atom 6 ist fur die Chromogenbildung belanglos. Es kann substituiert sein (vgl. S. 893) oder auch ganzlich fehlen 147), 119). 2V-Acetyl-L-rhamnosamin 144 a) und A-Acetyl-D-xylosamin 269) zeigen daher die Farbreaktion ebenfalls. 

It is not requisite that the anion eliminated in the step 19 to 20 be a hydroxyl ion, because acid hydrolysis of 5-amino-5-deoxy-l,2-0-isopropylidene - 3 - O - (methylsulfonyl )-a- D -xylofuranose likewise yields 3-pyridinol (21). On subjection to acid hydrolytic conditions which remove the 2V-acetyl group, such N-acetyl derivatives as 5-acetamido-5-deoxy-a-D-xylopyranose (see p. 167) are immediately transformed, through 17, into 3-pyridinol (21). Furthermore, acid hydrolysis of methyl 5-acetamido-5-deoxy-2,3,4-tri-0-methyl-a-D-... 

Table II. Product Yields in the y-Radiolysis of 2V-acetyl-DL-alanine...

Use of dimethoxydiphenylsilane in combination with N,N-dimethylformamide-p-toluenesulfonic acid to introduce silicon into the sucrose molecule has been exploited.27 On treatment with this combination of reagents, sucrose gave, after chromatographic fractionation of the acetylated mixture, 3,4,6,3, 4, 6 -hexa-0-acetyl-2,l -0-(diphenylsilyl)sucrose (10) and 3,4,3, 4 -tetra-0-acetyl-2,l 6,6 -di-0-(diphenylsilyl)sucrose (33) in 45 and 10% yield, respectively.27 With a view to introducing other heteroatoms, such as phosphorus or nitrogen, into the sucrose molecule, such reagents as dimethoxy-phenylphosphine, N,N-dimethylformamide dimethyl acetal, and 3,3-dimethoxypropylamine in combination with 2V,N-dimethylfor-mamide-p-toluenesulfonic acid are of interest. 

Biphenylenyl) - 3 - acetyl - 5-methyl-2,3-dihydro-1,3,4-oxadiazole (84) rearranges reversibly on warming to give the 2-(9-fluorenyl)-2V-diacetylhydrazone (85). 2-(Biphenylenyl)-3-benzoyl-5-methyl-2,3-di-... 

We looked at activity and the half-life of the derivatives, most of which were much less stable than the native protein. The only derivative we could make that was not any less stable was the acetimido derivative which has a positive charge and is also very small. But if we put an acetyl group on the 2V-terminal end, which destroyed the potential positive charge, we obtained an extremely unstable derivative. Although you can incorporate the iron and sulfur into the apoprotein and can crystallize the derivative ferredoxin, when you put this derivative into solution, you find that it decays very readily. Similarly, if we take oflF the carboxy terminal alanine and glutamine, one obtains a ferredoxin with much lowered stability. I find these results surprising. I didn t expect to find any difference in the stability of these derivatives. 

An improved synthesis of paromamine was effected with a Schiff base and a more protected 2-deoxystreptamine. The cyclohexylidene derivative of l,3-di-2V-(ethoxycarbonyl)-2-deoxystreptamine (79, race-mate) was condensed with 3,4,6-tri-0-acetyl-2-deoxy-2-(p-methoxy-benzylideneamino)-a-D-glucopyranosyl bromide (see Refs. 174 and 175 on p. 153) to give two products (80 and 81), which, after removal of the protecting groups, furnished paromamine (78) and an isomer, 6-0-(2-amino-2-deoxy-o-D-glucopyranosyl)-2-deoxystreptamine (82). The latter was devoid of antibacterial activity. 

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