By Tanmoy Kanti Das and Subhamoy Maitra
Read or Download Das Maitra - Cryptanalysis of Optimal Differential Energy Watermarking (DEW) and a Modified Robust Scheme PDF
Best chemistry books
Within the Bhopal catastrophe of 1984, nearly 2,000 citizens dwelling close to a chemical plant have been killed and 20,000 extra suffered irreversible harm to their eyes and lungs following the unintended free up of methyl isocyanate. This tragedy served to concentration overseas consciousness at the desire for governments to spot damaging elements and support neighborhood groups in making plans easy methods to care for emergency exposures.
- Catalysis in Asymmetric Synthesis (Postgraduate Chemistry Series)
- Topics in Current Chemistry (vol. 168)
- Die Beschäftigungssituation von wissenschaftlichem Nachwuchs
- Carbon Nanotubes:: A New Alternative for Electrochemical Sensors (Nanotechnology Science and Technology)
Additional info for Das Maitra - Cryptanalysis of Optimal Differential Energy Watermarking (DEW) and a Modified Robust Scheme
The difficulties encountered in the hydrolysis of 13-acyl ingenols are not uncommon for hindered tertiary hydroxy groups, while the unusual reactivity of the tertiary 13-hydroxy functionalities of phorbol might be mediated by acyl migration to the adjacent secondary C-12 hydroxy group. Acyl groups at the primary and allylic 20-hydroxy group can be selectively removed by solvolysis in acidic methanol . The rate of the reaction is critically dependent on the size of the ester group, sharply decreasing with the growing length of the acyl group.
Therefore, LiHMDS co-activates in a complementary fashion both the 3-hydroxylated site of ingenol 5,20-acetonide, by acting as a Brønsted base, and the acyl carbonyl of angelic anhydride, by behaving as a Lewis acid. Removal of the acetonide protection was uneventful, and I3A (5) was eventually obtained in 62% yield (Fig. 26). HNR2 O O R2N O O O ROH 117 R2N OR O 118 - HNR2 OR O O 119 120 Fig. 25 Possible mechanism of the angelate to tigliate isomerization during acylation reactions O O O 1. LHMDS, angelic anhydride (86%) acetone PTSA (73%) HO OH HO OH 3 (ingenol) 5 HO 2.
Esula E. cornigera E. esula E. kansui Ref.    [207, 214]               16-Hydroxyingenol Esters and 17-Hydroxyingenol Esters In the early studies on ingenoids, hydroxylation at C-16 was established based exclusively on considerations of chemical shift differences with the parent polyol ingenol. Whenever rigorous 2D-NMR measurements were done, the hydroxylation site on the geminal methyls was, however, always located at C-17.