110418-97-8Relevant academic research and scientific papers
Synthesis study toward mayamycin
Wu, Kui,Wang, Meining,Yao, Qizheng,Zhang, Ao
, p. 93 - 99 (2013/08/24)
Natural product mayamycin is the first example in the angucycline class featuring a C-glycoside linkage at the C5-position of the benz[a]anthracenone core with remarkable biological activities. We successfully synthesized the two retrosynthetic fragments, but found that the final C-glycosylation did not occur. Alternatively, an A-ring saturated aglycon was prepared, but the proposed C-glycosylation still did not proceed. Finally, a simplified substrate was used and the subsequent C-glycosylation went through smoothly, giving a two-ring less analogue of mayamycin. Natural product mayamycin is the first example in the angucycline class featuring a C-glycoside linkage at the C5-position of the benz[a]anthracenone core with remarkable biological activities. We successfully synthesized the two retrosynthetic fragments, but the final C-glycosylation did not occur. Instead, a two-ring less analog was success fully prepared, suggesting the steric effect played an important role in the synthesis of mayamycin. Copyright
On the synthesis of aminoglycosides of cardioactive steroids: A study directed towards β-selective glycosylations of 3-aminodigitoxose with digitoxigenin analogues
Finizia, Gabriella
, p. 75 - 98 (2007/10/03)
Carbamate derivatives of 3-aminodigitoxose (D-ristosamine) were prepared, with the purpose of synthesizing 3-amino-β-digitoxosyl derivatives of cardioactive steroids. A 1,3 participation procedure, used under acid or mercury salt catalysis, and the imidate procedure were investigated. A careful fine tuning of the glycosylation conditions was necessary in order to obtain significant β-D-stereoselectivity, which proved to be mainly dependent on the polarity of the solvent and the relative reactivity of the sugar and the nucleophile.
Studies of the Mechanistic Diversity of Sodium Cyanoborohydride Reduction of Tosylhydrazones
Miller, Vaughn P.,Yang, Ding-yah,Weigel, Theresa M.,Han, Oksoo,Liu, Hung-wen
, p. 4175 - 4188 (2007/10/02)
Reduction of tosylhydrazone derivatives of ketones and aldehydes with sodium cyanoborohydride in acidic medium is a mild, albeit versatile, deoxygenation reaction.The reaction mechanism has been proposed to proceed via either a direct hydride attack route or a tautomerization-then-reduction route.By using a mild reduction procedure (NaBH3CN, THF-MeOH, 0 deg C), it has been possible to stop the deoxygenation halfway and isolate the nascent tosylhydrazine product.Characterization of the resulting hydrazine to define the origin of the hydrogen being delivered to theformer carbonyl carbon has allowed us to unambiguously distinguish between these two possible mechanisms.Studies of reduction of tosylhydrazones derived from conjugated and saturated ketones confirmed earlier speculation that these reductions occur through a direct hydride attack mechanism.The reduction of para-substituted methyl phenyl ketone tosylhydrazones revealed a competition between these two mechanisms.Substrates bearing electron-donating substituents prefer to direct hydride attack pathway, while those with electron-withdrawing substituents favor an initial tautomerization prior to reduction.Sugar and hydroxyl ketone tosylhydrazones are also reduced by competing mechanisms.The mechanistic diversity in those cases may be attributed to the inductive effects compelled by the α substituents and the conformational constraints imposed by the ring structure.The mechanistic insights gained from these studies indicate that the direct hydride attack mechanism is the main reaction pathway due to the propensity of NaBH3CN to selectively attack the iminium ion.The tautomerization-then-reduction mechanism prevails only when the tautomerization of hydrazon to azohydrazine is facilitated.
