5′-Hydroxy-5′-homoaristeromycin: Synthesis and antiviral properties
0
Citation
9
Reference
10
Related Paper
Keywords:
Diastereomer
Side chain
The diastereomers of ketones 2 and 3 are shown to exhibit distinct photochemical reactivities due to conformational preferences; while the anti isomers of 2 and 3 undergo efficient Yang cyclization in 75−90% yields with a remarkable diastereoselectivity (> 90%), the syn isomers predominantly undergo Norrish Type II elimination. The differences in the product profiles of the diastereomers are consistent with a mechanistic picture involving the formation of precursor diastereomeric triplet 1,4-biradicals in which the substituents at α and β-positions stabilize the cisoid (cyclization) or transoid (elimination) geometry. The fact that such a diastereomeric relationship does indeed ensue at the triplet-excited-state itself is demonstrated via the nanosecond laser-flash photolysis of model ketones 1. The diastereomeric discrimination in the product profiles observed for ketones 2 and 3 as well as in the triplet lifetimes observed for ketones 1 can both be mechanistically traced back to different conformational preferences of the ground-state diastereomeric ketones and the intermediary 1,4-biradicals. Additionally, it emerges from the present study that the syn and anti diastereomers of ketones 2 and 3 represent two extremes of a broad range of widely examined butyrophenones, which lead to varying degrees of Yang photocyclization depending on the alkyl substitution pattern.
Diastereomer
Cite
Citations (25)
Subporphyrins B-Methoxy and B-phenyl β-sulfinylsubporphyrins have been separated into their diastereomers and their diastereomeric interconversions have been studied in various solvents, as reported by K. Yoshida and A. Osuka in their Full Paper on page 11727 ff. Diastereomeric interconversion of B-methoxy subporphyrin diastereomers takes place in protic solvents as the first experimental observation of bowl inversion of a subporphyrin, which likely proceeds by an SN1-type mechanism via a subporphyrin borenium cation.
Diastereomer
Cite
Citations (0)
Two diastereoisomers of isotricholomic acid (II), structural isomers of tricholomic acid (erythro-L-I) were synthesized from the corresponding diastereoisomers of β-hydroxyglutamic acid γ-ester (V) by the method for the synthesis of I. During the synthesis of II, the diastereoisomers of I were obtained by a novel intramolecular rearrangement.
Diastereomer
Cite
Citations (2)
Diastereomer
Cite
Citations (70)
Abstract A practical method for separation of the methyl esters of two diastereomeric, α-methylated, 2-azetidinon-4-ylacetic acid derivatives by selective dissolution using two solvents in which their relative solubilities are distinctly different is described. The less soluble diastereomer was first isolated from isopropanol in which the solubility of the more soluble diastereomer is 1.65 times that of the less soluble diastereomer. The more soluble diastereomer was then isolated from the mother liquor after a solvent switch to toluene in which the solubility of the more soluble diastereomer is only 1.15 times that of the less soluble diastereomer. The isolation cycle was then repeated to separate more of the diastereomers. This method is particularly useful for isolation of the more soluble component. A proposed explanation of the solubility differences suggests that the approach may be widely applicable to the separation of other structurally similar compounds.
Diastereomer
Cite
Citations (3)
Abstract Synthesizing compounds of the structure diastereomeric mixtures were obtained. If possible, the 31P chemical shifts and P[sbnd]P coupling constants of the individual diastereomers were determined from the 31P NMR spectra of these diastereomeric mixtures. In addition, the mixture of the seven diastereomers of bis(di-sec. butoxythiophosphoryl)disulfane was analyzed using shift-correlated 31P[sbnd]31P {1H}, 13C-31P {1H}, 13C-1H {31P} and 1H-1H {31P) 2D NMR spectra. In this way, the 31P, 13C and 1H chemical shifts and the corresponding coupling constants were assigned to the diastereomers. The appearance of regions of similar chemical shift into which the 1H, 13C and 31P signals of identical atoms or atom groups can be classified is characteristic of all the diastereomeric mixtures investigated. These regions can be explained mainly by the symmetry relations of a molecule moiety (sBuO)2P(S)S[sbnd].
Diastereomer
Chemical shift
Moiety
Coupling constant
Proton NMR
Cite
Citations (12)
Mitsunobu reaction
Solid-Phase Synthesis
Cite
Citations (53)
In the modern protocols of chemical protein syntheses, peptide‐α‐thioesters have been used as key components for the assembly of full‐length polypeptides through chemoselective peptide coupling reactions. A variety of thioester precursors have been developed for the synthesis of the peptide‐α‐thioesters by Fmoc solid phase peptide synthesis (Fmoc‐SPPS). Recently our group found a peptidyl‐ N ‐acetylguanidine as a new peptide‐α‐thioester precursor. This peptide derivative can be converted into a corresponding peptide‐α‐thioester only by treatment with an excess amount of a thiol in aqueous buffers at around neutral pH. This unique property allowed us to envision the practical use of the peptidyl‐ N ‐acetylguanidines for the chemical syntheses of proteins; however, an efficient synthetic method has been lacking. Herein, we report an efficient solid‐phase synthesis of peptidyl‐ N ‐acetylguanidines. This new synthetic method employing selective activation and cleavage of a peptide bond successfully provided peptidyl‐ N ‐acetylguanidines from the on‐resin protected peptides prepared by standard Fmoc‐SPPS. We also evaluated the reactivity of a peptidyl‐ N ‐acetylguanidine in native chemical ligation through the synthesis of glucose‐dependent insulinotropic polypeptide analogue. Copyright © 2016 European Peptide Society and John Wiley & Sons, Ltd.
Thioester
Native chemical ligation
Chemical Ligation
Peptide Synthesis
Solid-Phase Synthesis
Cleavage (geology)
Peptide bond
Cite
Citations (7)
Diastereomer
Derivative (finance)
Cite
Citations (0)
Diastereomer
Proton NMR
Cite
Citations (42)