- Total syntheses of (?)-emestrin H and (?)-asteroxepin
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First total syntheses of (?)-emestrin H and (?)-asteroxepin are described. To find the appropriate protecting group on the amide nitrogen of the diketopiperazine core, we conducted model studies using a simple diketopiperazine derivative. As a result, allyloxymethyl (Allom) group was the most suitable protecting group, which tolerated Nicolaou's sulfenylation conditions, and was easily cleavable under the mild conditions using Pd(PPh3)4 and N,N-dimethylbarbituric acid leaving methylthioethers intact. The general utility of Allom group for protection of amides was studied using simple substrates. Finally, the effectiveness of Allom group was proved by the accomplishment of the first total synthesis of (?)-emestrin H. Allom group was robust enough during installation of two methylthioethers to the diketopiperazine core and easily removed at the final step. The first total synthesis of (?)-asteroxepin was also completed by acylation of (?)-emestrin H.
- Sakata, Juri,Tokuyama, Hidetoshi,Ueda, Yusuke,Umeki, Kanato
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- Synthesis of valganciclovir hydrochloride congeners
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Valganciclovir hydrochloride (1) is used for the treatment of cytomegalovirus (CMV) retinitis in patients with weakened immune systems. Valganciclovir hydrochloride is a hydrochloride salt of L-valyl ester of ganciclovir (2) that exists as a mixture of two diastereomers. According to the U.S. Food and Drug Administration specifications, the diastereomeric ratio of valganciclovir hydrochloride 1 should be maintained in the range 55:45 to 45:55. According to the U.S. Food and Drug Administration specifications, the diastereomeric ratio of valganciclovir hydrochloride 1 should be maintained in the range 55:45 to 45:55. During the process development of valganciclovir hydrochloride, six related substances (impurities) were observed along with the final active pharmaceutical ingredient. Among these six impurities, ganciclovir (2) and guanine (3) are the key starting materials and degraded impurities of ganciclovir, respectively. The remaining four impurities were identified as isovalganciclovir hydrochloride (4), methoxymethylguanine (5), O-acetoxy ganciclovir (6), and isovalarylganciclovir (7). The present work describes the synthesis and characterization of these four impurities.
- Babu, K. Srihari,Rao, M. Raghavendar,Goverdhan,Srinivas,Reddy, P. Pratap,Venkateswarlu,Anand, R. Vijaya
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p. 1751 - 1758
(2013/05/22)
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- Alternative synthesis of 9-{3-[(diisopropoxyphosphoryl)-methoxy]-2- hydroxypropyl}adenine and its free phosphonates substituted at the c-8 position of purine base
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For its high therapeutic effect, (S)-9-[3-hydroxy-2-(phosphonomethoxy) propyl]adenine (HPMPA) is an important member of a class of acyclic nucleoside phosphonates (ANPs). Although its constitutional isomer, 9-[2-hydroxy-3- (phosphonomethoxy)propyl]adenine (iso-HPMPA), exhibits no antiviral activity, our general interest in C-8 substituted adenine ANPs led us to prepare certain iso-HPMPA derivatives modified at the C-8 position of adenine. Novel alkylating agent, diisopropyl {[2-(tetrahydro-2-pyranyl)oxy-3-tosyloxypropoxy]-methyl} phosphonate (9), was prepared by procedure starting from allyl alcohol (4). 9-{3-[(Diisopropoxyphosphoryl)methoxy]-2-hydroxypropyl}adenine (12) was prepared by alkylation of adenine with the alkylating agent 9 followed by acid hydrolysis, although elimination by-product 9-{3-[(diisopropoxyphosphoryl) methoxy]prop-1-enyl}adenine (11) predominated in the reaction mixture. Bromination of the compound 12 gave 8-bromoadenine derivative 13 quantitatively. Nucleophilic substitutions of the bromine atom of compound 13 with N-and O-nucleophiles, followed by phosphonate deprotection, afforded the free phoshonic acids 15-18.
- Janeba, Zlatko,Masojidkova, Milena,Holy, Antonin
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experimental part
p. 371 - 381
(2010/07/09)
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- Sparteine-mediated enantioselective [2,3]-Wittig rearrangement of allyl ortho-substituted benzyl ethers and ortho-substituted benzyl prenyl ethers
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The (-)-sparteine-mediated enantioselective [2,3]-Wittig rearrangement of N,N-dialkyl-o-allyloxymethylbenzamides and o-substituted benzyl prenyl ethers has been investigated. Enantiomeric excess up to 60% was observed as for the reaction with N,N-diethyl-o-allyloxymetylbenzamide. From the mechanistic investigations, it was suggested that the stereoinformation was introduced at the deprotonation step. Substoichiometric amount of (-)- sparteine (0.2 equiv.) did not decrease the enantioselectivity. Introduction of functional groups other than carbamoyl group did not enhance the enantioselectivity in this rearrangement.
- Kawasaki, Takeshi,Kimachi, Tetsutaro
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p. 6847 - 6862
(2007/10/03)
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- SYNTHESIS OF A NEW POTENTIAL ANTIVIRAL AGENT - 9-ALLYLOXYMETHYLGUANINE
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A convenient method has been developed for the synthesis of 9-allyloxymethylguanine. The direct alkylation of the trimethylsilyl derivative of guanine allyloxymethyl chloride gives a 64 percent yield of 9- and 7-allyloxymethylguanine (3:1). A mixture of 9- and 7-allyloxymethyl-N-acetylguanine (7:4) can be obtained in 56 percent yield by the condensation of diacetylguanine with allyloxymethyl acetate in dimethyl sulfoxide in the presences of p-toluenesulfonic acid.
- Ozerov, A. A.,Brel', A. K.
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p. 945 - 948
(2007/10/02)
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- TRINITROETHYL ETHERS OF SUBSTITUTED ALCOHOLS
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The influence of the trinitromethane salt cations and the substituents in the alkyl moiety of chloromethyl ethers of alcohols on the yields of trinitroethyl ethers of the substituted alcohols formed from them was established.On this basis a representative series of previously unavailable trinitroethanol ethers was synthesized.
- Luk'yanov, O.A.,Pokhvisneva, G.V.
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p. 2217 - 2221
(2007/10/02)
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- 1-Methoxy-1-methyl-3-{p-[(1,1-dimethyl-2-propynyloxy)-methoxy]phenyl}urea
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This invention relates to novel (alkenyloxy), (alkynyloxy) and (cyanoalkoxy) alkoxyphenyl ureas and their use as herbicidal agents.
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