Deacetylation, selective

Acetates. Because of the significant interest in selective acetylation reactions of sucrose, the need for a convenient and unambiguous method of identification has been recognized (34,35). The position of an acetyl group in a partially acetylated sucrose derivative can be ascertained by comparison of its H-nmr acetyl methyl proton resonances after per-deuterioacetylation with those of the assigned octaacetate spectmm. The synthesis of partially acetylated sucroses has generally been achieved either by way of selectively protected derivatives such as trityl ethers and cychc acetals or by direct selective acetylation and deacetylation reactions. 

Systems with different selectivity were nsed for the separation of 10-deacetyl-baccatin III (10 DAB 111) from yew extracts [69]. A silica column with stepwise gradient elution with aqneous methanolic mobile phases can be nsed for separation of the taxoid fraction from nonpolar materials, partial separation of the taxoid fraction into a polar one (containing 10-DAB 111), and for a medinm polarity taxoid fraction (containing paclitaxel and cephalomannine). Most polar material (tannins... 

Different oxidation states of sulfur have also been explored, particularly sulf-ones and sulfonamides as transition state analogs of lysine deacetylation, but without much success. The monodentate SAHA-like methyl sulfoxide 7 proved most potent, but still with an enzyme IC50 of only 48 pM and indications of HDAC/TDAC selectivity in cellular assays [28]. 

N. N. Sertkaya, J. W. Gorrod, In vitro Deacetylation Studies with Isomeric Acetamid-obiphenyls Using Selective Carboxylesterase Inhibitors , Anticancer Res. 1988, 8, 1345-1350. 

Acetylated isoforms of H3 and H4 are often the targets of ongoing methylation [126,150,151,217,218]. In chicken immature erythrocytes, rapidly acetylated and deacetylated H3 and H4 are selectively methylated, while in Hela cells dynamically acetylated H3, but not H4, is methylated [150,219,220]. H4 that is slowly acetylated and deacetylated is methylated in HeLa [150]. Acetylated yeast H3 was preferentially methylated at Lys-4 [138]. These studies suggested that the processes of histone methylation and dynamic acetylation are not directly coupled, with neither modification predisposing H3 or H4 to the other [138,220]. 

Thus, Xi exemplifies both extremes of the histone code, namely the general deacetylation of all four core histones and the specific retention of H3 dimethylated at lysine 9/27. It also illustrates the great stability of epigenetic signals carried by the histone tails. The general underacetylation of Xi, the undermethylation of H3 lysine 4 and the selective retention of H3 dimethylated at lysine 9/27, are all maintained in human x hamster somatic cell hybrids in which Xi is the only human chromosome and therefore exists in an almost completely foreign (i.e., hamster) cellular environment [73]. 

Finally, the deacetylation of histones in methylated gene regions may be selective with respect to the histone affected. Chromatin immunoprecipitation analysis of the histone acetylation status of proviral sequences targeted to defined genome loci in MEL cells showed that the in vitro methylated proviral sequences that were transcriptionally silent in vivo, were hypoacetylated only with respect to histone H3 in contrast, the acetylation status of histone H4 was comparable on the methylated and unmethylated provirus [78]. Moreover, the H3 acetylation status correlated closely with the location of methylated CpGs along the proviral sequence. 

Comparative Antitumor Activity of Selected 4-Deacetyl vinblastine Amides against Several Murine Tumor Models... 

Haggarty, S.J., Koeller, K.M., Wong, J.C., Grozinger, C.M. and Schreiber, S.L. (2003) Domain-selective small-molecule inhibitor of histone deacetylase 6 (HDAC6)-mediated tubulin deacetylation. Proceedings of the National Academy of Sciences of the United States of America, 100, 4389 394. 

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