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1.
[reaction: see text] A synthesis of the C(43)-C(67) fragment of amphidinol 3 (AM3) has been accomplished by a route that features the use of a double allylboration reaction for synthesis of 1,5-diol 4b, which serves as a precursor to dihydropyran 11. 相似文献
2.
Certain (Z)-1,5-syn-diols 2 may be converted into 2,6-trans-5,6-dihydropyrans by using phosphonium salt 4 or phosphorane 5 as dehydrating agents. A more general four step procedure converts the (Z)-1,5-syn-endiols into enantiomeric dihydropyrans ent-3 via regioselective silylation of the allylic alcohol unit followed by mesylate formation and base-promoted nucleophilic displacement. 相似文献
3.
Semiclassical calculations on diatomic type models are presented in order to account for the kinetic energy released in the metastable dissociation of the CH4+ and CD4+ ions; the discrete structure of the metastable peaks is considered. 相似文献
4.
Subreactions in the Chloramine Preparation. In the preparation of chloramine from solutions of ammonia and sodium hypochlorite there is considerable overchlorination, resulting in the formation and subsequent decomposition of dichloramine. Nitrogen, chloride ion, and hypochlorite ion are formed in the decomposition of dichloramine; in the presence of certain organic compounds the products of chlorination via radicals are observed. Chloramine is obtained in over 90% yield by neutralizing the alkali formed in the reaction of ammonia with hypochlorite. Etheral solutions of dichloramine are prepared from chloramine solutions by treatment with phosphate buffer. 相似文献
5.
J.P. Flamme H. Wankenne R. Locht J. Momigny P.J.C.M. Nowak J. Los 《Chemical physics》1978,27(1):45-49
The metastable transitions producing CH33/CH4 and CD3+/CD4 have been investigated by means of translational spectroscopy. For the first time structures are observed in a metastable peak corresponding to the dissociation of a polyatomic ion. They are interpreted by tunneling through a rotational barrier from discrete quasi-bound states. Kinetic energy releases have been measured. 相似文献
6.
The momentum distributions of He+ fragments from photodissociation of He+2 ions have been recorded in a crossed-beams experiment. The discrete values of the kinetic energy releases can be predicted from the vibrational spacings in the ground state of the primary ions. 相似文献
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8.
Sammis GM Flamme EM Xie H Ho DM Sorensen EJ 《Journal of the American Chemical Society》2005,127(24):8612-8613
A new 1-hydrazinodiene (1) has been developed and utilized in Lewis acid catalyzed, intermolecular Diels-Alder reactions with various electron-deficient alkenes. The hydrazine can then be deprotected, and a molecule of methanesulfinic acid is eliminated to provide a putative diazene intermediate (4), which then spontaneously undergoes a suprafacial 1,5-sigmatropic shift to yield stereochemically complex cyclohexenes. This method has been applied to the synthesis of a constitutionally and stereochemically complex decalin derivative. 相似文献
9.
[structure: see text] A synthesis of the C(1)-C(25) fragment of amphidinol 3 is described. The synthesis features two applications of double allylboration reaction methodology for the highly stereoselective synthesis of 1,5-diol units in the C(1)-C(15) segment. 相似文献
10.
Zuo Chao Shi Wei-Wei Chen Xiao-Xu Glatz Marie Riedl Bernd Flamme Ingo Pook Elisabeth Wang Jiawei Fang Ge-Min Bierer Donald Liu Lei 《中国科学:化学(英文版)》2019,62(10):1371-1378
Blockade of the interaction of anaphylatoxin C5a with its receptor C5aR1 has been actively studied as a potential treatment for many inflammatory diseases; but current C5a antagonists exhibit inadequate potency and poor species cross-reactivity, and novel biochemical tools are needed to investigate whether the core region of C5a contains important interaction epitopes that can explain these limitations. Herein, we report the development of chimeric protein C5a probes containing both the complete core region of rat or human C5a, and the small-molecule antagonist PMX53-1. These probes were chemically synthesized through hydrazide-based native chemical ligation of a linear peptide hydrazide with the requisite cyclopeptidic antagonist, both of which were made by solid-phase synthesis. Quasi-racemic X-ray crystallography established that attachment of PMX53-1 did not affect the structure of the core region of C5a. Subsequent C5aR1 activity assays demonstrated the probes can provide valuable insights into the development of C5a antagonists; for example, they exhibited significantly better binding affinity and much improved species cross-reactivity than PMX53-1, supporting the notion that the effect of some epitopes outside the C-terminus of C5a should be taken into consideration when designing better C5a antagonists. Surprisingly, the core region of C5a was found to partially agonize C5aR1, suggesting the presence of more than one agonistic interaction in the binding of C5a to C5aR1. This study exemplifies the value of chemical protein synthesis in developing novel receptor probes for drug discovery research. 相似文献