An original synthetic strategy is presented for the preparation of the sensitive 3‐amino‐4‐hydroxypyrrolidinone‐4‐acetic acid residue that is present in the structures of the microsclerodermin ...natural product family. The approach relies on the use of a linear γ‐amino acid surrogate, derived from asparagine, bearing a β‐dithiolanyl group. A protected dipeptide model system is used to demonstrate that selective removal of the dithioketal protection followed by cyclization gives the target structure in single diastereoisomer form and with little or no dehydration.
3‐Amino‐4‐hydroxypyrrolidinone‐4‐acetic acid appears in the structures of the microsclerodermin natural product family and represents a challenging synthetic target, due to the ease with which it can dehydrate. We describe a successful strategy for the creation of this unusual γ‐amino acid in a model dipeptide, through liberation of a ketone from a dithiolane precursor followed by facile cyclization in mild conditions.
Based on the Tf2O‐mediated intermolecular reaction of secondary amides with enamines derived from ketones, a novel approach to β‐enaminones has been developed. The reaction is widely functional group ...tolerant and highly chemoselective. In the presence of 4 Å molecular sieves, the method can be extended to the one‐pot condensation of secondary amides with ketones for NH β‐enaminones synthesis.
A novel approach to β‐enaminones has been developed, based on a Tf2O‐mediated reaction of secondary amides with ketones enamines. The method can be extended to the one‐pot condensation of secondary amides with ketones for β‐enaminones synthesis.
A direct transformation of secondary amides into α‐branched ketones with enamines as soft alkylation reagents was developed. In this reaction, enamines serve as surrogates of alkyl carbanions, rather ...than the conventional enolates equivalents in the Stork's reactions, which allowed for the easy introduction of alkyl groups with electrophilic functional groups. In the presence of 4 Å molecular sieves, the method can be extended to the one‐pot coupling of secondary amides with aldehydes to yield ketones.
There has been extensive research into lithium-rich layered oxide materials as candidates for the nextgeneration of cathode materials in lithium-ion batteries, due to their high energy density and ...low cost; however, their poor cycle life and fast voltage fade hinder their large-scale commercial application. Here, we propose a novel cation/anion (Na+/PO43-) co-doping approach to mitigate the discharge capacity and voltage fade of a Co-free Li1.2Ni0.2Mn0.6O2 cathode. Our results show that the synergistic effect of cation/anion doping can promote long cycle stability and rate performance by inhibiting the phase transformation of the layered structure to a spinel or rock-salt structure and stabilizing the well-ordered crystal structure during long cycles. The co-doped sample exhibits an outstanding cycle stability (capacity retention of 86.7% after 150 cycles at 1 C) and excellent rate performance (153 mAh g−1 at 5 C). The large ionic radius of Na+ can expand the Li slab to accelerate Li diffusion and the large tetrahedral PO43- polyanions with high electronegativity stabilize the local structure to improve the electrochemical performance.
Secondary amides are a class of highly stable compounds serving as versatile starting materials,intermediates and directing groups（amido groups） in organic synthesis.The direct deacylation of ...secondary amides to release amines is an important transformation in organic synthesis.Here,we report a protocol for the deacylation of secondary amides and isolation of amines.The method is based on the activation of amides with Tf_2O.followed by addition of organocerium reagents,and acidic work-up.The reaction proceeded under mild conditions and afforded the corresponding amines,isolated as their hydrochloride salts,in good yields.In combination with the C-H activation functionalization methodology,the method is applicable to the functionalization of aniline as well as conversion of carboxylic derivatives to functionalized ketones.
A new strategy to construct allylamines through reductive alkenylation of secondary amides with enamines is reported. The method features the use of trifluoromethanesulfonic anhydride as an ...activation reagent of amides, and enamines as unconventional alkenylation reagents. In this manner, enamines serve as surrogates of alkene carbanions instead of the classical enolates equivalents. A possible mechanism involving a Hoffmann-like elimination of the amine–borane complex intermediate is proposed.
Alisol B 23-acetate （AB23A） is a natural triterpenoid isolated from the traditional Chinese medicine rhizoma alismatis, which exhibits a number of pharmacological activities, including anti-hepatitis ...virus, anti-cancer and antibacterial effects. In this study we examined whether AB23A protected against non-alcoholic steatohepatitis （NASH） in mice, and the mechanisms underlying the protective effects. NASH was induced in mice fed a methionine and choline-deficient （MCD） diet for 4 weeks. The mice were simultaneously treated with AB23A （15, 30, and 60 mg.kg^-1.d^-1, ig） for 4 weeks. On the last day, blood samples and livers were collected. Serum liver functional enzymes, inflammatoru markers were assessed. The livers were histologically examined using H＆E, Oil Red O, Masson＇s trichrome and Sirius Red staining. Mouse primary hepatocytes were used for in vitro experiments. The mechanisms underlying AB23A protection were analyzed using siRNA, qRT-PCR, and Western blot assays. AB23A treatment significantly and dose-dependently decreased the elevated levels of serum ALT and AST in MCD diet-fed mice. Furthermore, AB23A treatment significantly reduced hepatic triglyceride accumulation, inflammatory cell infiltration and hepatic fibrosis in the mice. AB23A-induced decreases in serum and hepatic jipids were related to decreased hepatic lipogenesis through decreasing hepatic levels of SREBP-1c, FAS, ACC1 and SCD1 and increased lipid metabolism via inducing PPARa, CPTlc（, ACADS and LPL. The reduction in inflammatory cell infiltration corresponded to deceased serum levels of mKC and MCP-1 and decreased hepatic gene expression of MCP-1 and VCAM-I. The reduction in hepatic fibrosis was correlated with decreased hepatic gene expression of fibrosis markers. The protective effects of AB23A were FXR-dependent, because treatment with the FXR agonist CDCA mimicked AB23A-induced hepato-protection in the mice, whereas co-administration of FXR antagonist guggulsterone abrogated AB23A-induced hepato-protection. In mouse primary hepatocytes, FXR gene silencing abrogated AB23A-induced changes in gene expression of Apo C-II, CPT1α, ACADS and LPL. AB23A produces protective effects against NASH in mice via FXR activation.
Two new phenethanol glycosides,named ligurobustoside P（1）,ligurobustoside Q（2） have been isolated from the leaves of Ligustrum robustum,together with the known compound angoroside A（3） which was ...firstly isolated from this species.The structures of the two new phenethanol glycosides（1-2） were elucidated by a combination of high-resolution electron ionization mass spectrometry（HR-ESI-MS）,~1H NMR,~（13）C NMR,HMQC,and HMBC spectra for the first time.
Based on the Tf
2
O‐mediated intermolecular reaction of secondary amides with enamines derived from ketones, a novel approach to β‐enaminones has been developed. The reaction is widely functional ...group tolerant and highly chemoselective. In the presence of 4 Å molecular sieves, the method can be extended to the one‐pot condensation of secondary amides with ketones for NH β‐enaminones synthesis.
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