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Received Jun 8; Accepted Jul This article has been cited by other articles in PMC. Abstract Screening of ligand molecules to target proteins using computer-aided docking is a critical step in rational drug discovery. Based on this circumstance, we attempted to develop a virtual screening application system, named VSDK Virtual Screening by Docking, which can function under the Windows platform. This is a user-friendly, flexible, and versatile tool which can be used by users who are familiar with Windows OS.
A couple of years earlier, the preparation of benzazocines 66 was accomplished from terminal 1,9-enynyl esters 63 through a gold-catalyzed cascade reaction. Xie et al proposed the initialization of the mechanism with a 1,2-acyloxy shift that further evolves with a O-cyclization to yield 1,3-dipolar intermediates Two different diastereoisomers were isolated and fully characterized, the trans isomers 66 being the major products of the reaction Figure 6B Feng et al. The same group has reported on the successful attempts to obtain complex tetracyclic frameworks by appliying a similar gold-catalyzed protocol on related linear enynyl esters Sun et al.
Liu et al. First, the gold I -complex activates the alkyne group to facilitate a 1,3-acyloxy migration leading to the allene intermediates Further along into the mechanistic pathway, the metal acts as Lewis acid promoting the intramolecular Ferrier reaction with the departure of the alcoxy group, which is integrated as a new ligand in the gold complex [Au]OR2 furnishing the oxocarbenium species Lastly the bicyclic structure of 70 is formed by cyclization and formation of AcOR2 as a by-product Liao et al.
Gold-mediated cycloisomerization of 1,n-dienynes started by an acyloxy shift process. An unusual chemoselective gold-activation of alkenes over allenes using sterically bulky ligands as ditBuXphos has been described by Shi et al. Substituted bicyclic[4. As in the case of 1,n-enynes, reactions initiated by migration of a carbonate or ester group have been subject of study in related 1,n-diyne derivatives Day and Chan, ; Li et al.
Chan et al. In the latter, therefore a cationic catalyst featuring a N-heterocyclic carbene ligand is used. In both cases the mechanistic route would be initiated by the gold-activation of the propargyl moiety promoting a 1,3-acyloxy transfer followed by several cyclizations.
In fact, the relative position of the olefine moiety determines whether the evolution of the mechanisms at the first cyclization occurs through either a 1,4-eneallene cycloisometization toward 80 or a metallo-Nazarov cyclization toward the tetracycles In , the synthesis of naphtho[2,3-c]furan-1 3-H -ones 84 was reported via cycloisomerization of propargylic ynoates 83, under thermal conditions with BrettPhosAuCl as catalyst and in presence of NaBAr 4 F as an activator of the gold complex Figure 8B Li et al.
The reaction mechanism would involve a [3,3]-rearrangement of the propargyl ester leading to a carboxyallene intermediate followed by an intramolecular Diels-Alder cyclization. The authors were able to synthesize up to 24 examples of 84 combining diverse alkyl and aryl substituents and they also describe a new method for the in-situ generation of carboxyallene intermediates.
Gold-mediated cycloisomerization of 1,n-diynes started by an acyloxy shift process. An interesting formation of primitive dendrimer systems containing bicyclic structures from substrates incorporating two sets of dialkynes were described by Oh et al. The hydrated NaAuCl4 mediates in the thermal cycloisomerization of 85 trough a dual 1,3- and 1,2-acyloxy transposition at the terminal and inner alkyne moieties, respectively, followed by an annulation process leading to the benzo-fused 7-member cycles 86 Figure 8C Lee et al.
The authors were able to resolve the diasteromeric mixture and even extend this protocol to other diynes in which the pivaloate substituents are located at positions 3 and 3' Lee et al.
Gold-Catalyzed Cycloisomerization Processes of 1,n-enynes and 1,n-diynes Initiated by a Nucleophilic Attack Onto the Alkyne Group Gold is able to activate an alkyne group toward a nucleophilic addition and, for instance, make it susceptible to act as the receptor motif in a hydride shift reaction Xie et al.
In this sense, Wong et al. This mechanistic proposal is supported by deuterium-labeling cross-over experiments. According to the authors, there is no precedent of cycloisomerizations initiated by a gold-catalyzed 1,6-hydride transfer reaction.
This protocol provides rapid access to fused polycyclic compounds presented in many bioactive natural products as Nominine or Walsuranin B. Gold-mediated cycloisomerization reactions of 1,n-enynes containing an internal atom-centered nucleophile. An activated alkyne group could act as electrophile in an intramolecular nucleophilic attack if a functional group present within the system has such nature. An experimental gold I -mediated double 6-endo cascade cyclization strategy of enynes 92 to form benzoxanthenone and benzoacridone derivatives 93 has been described by Cheng et al.
Figure 9B. Likewise, gold III -complexes have been reported to be excellent catalysts in similar transformations. Kumar et al. Besides, the use of bimetallic complexes has become more popular in gold chemistry during the last years El Sayed Moussa et al. Recently, Zi et al. Several reports pivoting about cycloisomerization reactions of enyne-lactones by gold I -catalysis have been published by Zhu et al.
Figure The presence of the benzo-fused ring at intermediates displaces the equilibrium reaction toward the most stable 2-oxoninium a, whereas, in its absence, intermediate b is the preferred product.
The addition of one equivalent of water is required for the formation of 99 whereas the diester is isolated even in anhydrous media Figure 10A Luo et al. On the other hand, the nature of the ligand at the gold I -catalyst seems to have a high influence in the evolution of the mechanism allowing the transformation of related enyne-lactones With this set of papers Zhu et al.
Gold-mediated cycloisomerization of enyne-lactones. Lamellarins are a group of pyrrole alkaloids based in a pyrano[3,4-b]pyrrol-7 1H -one scaffold which present anticancer activity. Thibonett et al. The former cyclization proceeds involving the amine group in the formation of the pyrrol ring, whereas in the latter it is one of the ester groups who is involved in the formation of the pyranone ring Delaye et al.
Gold-mediated cycloisomerization of 1,n-diynes containing an internal atom-centered nucleophile. In , Xu et al. Thus, 1,6-diynes undergo a 6-exo-dig cyclization with the carbonyl oxygen of the amide group leading to the 1,3-oxazine gold intermediate , which is then intercepted by the remaining alkyne affording the intermediate Otherwise, 1,6-diynes bearing ortho-benzyl alcohols evolve to dihydroisobenzofuran derivatives trough a gold I -catalyzed protocol initiated by two consecutive unsual 5-exo-dig hydroxyalkilation processes and a further Prins-like cyclization.
Authors reasoned the formation of the 5-exo-dig cyclized product taking into account the more favorable six-membered ring chelated gold complex when compared to the alternative bigger chelate, which would result in a more usual 6-endo-O-cyclization Figure 11C Hashmi et al.
Thus highlighting that an approach towards day care fundoplication had begun whilst the possibility of day care cholecystectomy had already become evident and been brought into practice.
Simple acceptances of a procedure to be performed as day care needs to have no increased morbidity and mortality compared to inpatient procedure, high success rate of same-day discharge and satisfied patients. Good pain relief can be brought in by local infiltration of the diaphragm as well as port site wounds supplemented by NSAIDs or likewise .
Recently new interventions to treat GERD have been developed like the magnetic sphincter positioned around the distal esophagus laparoscopically . Here post operative pain is almost negligible since the dissection is minimal. Thus pain relief becomes a major criterion for deciding the feasibility of the surgical procedure to be considered as a day care procedure.
The Nissen Rossetti fundoplication differs from the usual Nissen fundoplication in not having the divide the short gastric vessels during the fundic wrap creation. All the other operative steps are similar.
This reduces the operative time and also decreases the blood loss in the surgery. In normal individuals this would even add to decreased post operative pain since the dissection is less than the nissen fundoplication procedure.
The De Meester score post operatively for the result of the procedure can assess the efficacy of the procedure. On the other hand, docking application tools, in which the ligand-macromolecule interaction conformation is predicted and scored in terms of binding free energy between the ligand and macromolecule, have made a remarkable progress in their accuracy and speed, although molecular docking is an extremely demanding task for computer resources.
There is no question about the fact that the CAMD computer-aided molecular design approach is becoming a common practice in drug discovery and development [ 1 ]. Owing to all these advancements in structure data bases and application software, a highthrough- put virtual screening technology, in which one can screen thousands of compounds for their binding affinity against a target macromolecule, has been developed and utilized to aid in the drug discovery.
Indeed, virtual screening tools have been reported in the literature [ 2 , 3 ]. However, there exist various constraints such as strict computer hardware requirements, demands for highlytechnical computer knowledge, complex operation steps, and user-unfriendly procedures. Herein, we have developed a virtual screening application system which functions under the Windows environment.
This is a user-friendly, flexible, and versatile tool which can be used by anybody who is familiar with Windows OS.