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Moriarty RM Rani N Enache LA Rao MS Batra H Guo L Penmasta RA Staszewski JP Tuladhar SM Prakash O Crich D Hirtopeanu A Gilardi R 《The Journal of organic chemistry》2004,69(6):1890-1902
A general and novel solution to the synthesis of biologically important stable analogues of prostacyclin PGI(2), namely benzindene prostacyclins, has been achieved via the stereoselective intramolecular Pauson-Khand cyclization (PKC). This work illustrates for the first time the synthetic utility and reliability of the asymmetric PKC route for synthesis and subsequent manufacture of a complex drug substance on a multikilogram scale. The synthetic route surmounts issues of individual step stereoselectivity and scalability. The key step in the synthesis involves efficient stereoselection effected in the PKC of a benzoenyne under the agency of the benzylic OTBDMS group, which serves as a temporary stereodirecting group that is conveniently removed via benzylic hydrogenolysis concomitantly with the catalytic hydrogenation of the enone PKC product. Thus the benzylic chiral center dictates the subsequent stereochemistry of the stereogenic centers at three carbon atoms (C(3a), C(9a), and C(1)). 相似文献
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Stereoselective and efficient synthesis of respective aminocyclitol moieties 1a and 2a of trehazolin and trehalostatin as hexaacetates 1b and 2b using ring-closing enyne metathesis as the key reaction is described. 相似文献
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Richard Gilardi Clifford George Jerome Karle Philip E. Eaton Munagala Rao 《Journal of heterocyclic chemistry》1993,30(5):1389-1391
Despite the angular strain associated with the assembly of small rings, 1,2-diisocyanatocubane reacts with trimethylsilyl azide under mild conditions to form a hexacyclic ring assembly that contains an imidazolidone ring fused to one edge of cubane. This compound was identified as an azidocarbonyl-substituted cubanourea by means of X-ray crystal structure analysis of the nitro-derivative, the energetic compound N-azidocarbonyl-N1-nitrocubanourea. 相似文献
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Baral Pratibha Munagala Meghana Shastri Yogendra Kumar Vinod Agrawal Deepti 《Cellulose (London, England)》2021,28(10):6305-6322
Cellulose - In an enzymatically driven lignocellulosic biorefinery, pretreatment and hydrolysis modules are the two most significant cost contributors for obtaining high gravity sugar solutions.... 相似文献
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Sudipto Guha Adam Meyerson Kamesh Munagala 《Journal of Algorithms in Cognition, Informatics and Logic》2003,48(2):429-440
We consider a generalization of the classical facility location problem, where we require the solution to be fault-tolerant. In this generalization, every demand point j must be served by rj facilities instead of just one. The facilities other than the closest one are “backup” facilities for that demand, and any such facility will be used only if all closer facilities (or the links to them) fail. Hence, for any demand point, we can assign nonincreasing weights to the routing costs to farther facilities. The cost of assignment for demand j is the weighted linear combination of the assignment costs to its rj closest open facilities. We wish to minimize the sum of the cost of opening the facilities and the assignment cost of each demand j. We obtain a factor 4 approximation to this problem through the application of various rounding techniques to the linear relaxation of an integer program formulation. We further improve the approximation ratio to 3.16 using randomization and to 2.41 using greedy local-search type techniques. 相似文献
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A stereoselective total synthesis of leiocarpin C ( 2 ) and (+)‐Goniodiol ( 1 ) by applying olefin cross‐metathesis and substrate directed dihydroxylation as the key steps is reported (Scheme 3). 相似文献
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