Chiral Brønsted Base Activation of Donor-Acceptor Cyclopropanes toward Diastereo- and Enantioselective [3 + 2] Cycloaddition with Isatin-Derived Ketimines.

Organocatalyzed diastereo- and enantioselective [3 + 2] cycloaddition reactions of donor-acceptor (D-A) cyclopropanes with isatin-derived ketimines are presented. Different from well-developed Lewis acid activation protocols which promote the reactivity of D-A cyclopropanes through coordinating to the acceptor group, in this reaction, dicyanocyclopropylmethyl ketones can be activated through nucleophilic activation of the donor group by using dihydroquinine-derived squaramide as Brønsted base catalyst. The reaction affords functionalized spiro[oxindole-3,2'-pyrrolidines] with two nonadjacent tetra- and tri-substituted stereocenters in 83-99% yields, moderate to excellent diastereoselectivities (up to >20:1 diastereomeric ratio (dr)), and excellent enantioselectivities (up to >99% enantiomeric excess (ee)) under mild conditions.

Catalytic Asymmetric Synthesis of Unnatural Axially Chiral Biaryl δ-Amino Acid Derivatives via a Chiral Phenanthroline-Potassium Catalyst-Enabled Dynamic Kinetic Resolution.

Axially chiral biaryl δ-amino acids possess significantly different conformational properties and chiral environment from centrally chiral amino acids, therefore, have drawn considerable attention in the fields of synthetic and medicinal chemistry. Herein, a novel chiral phenanthroline-potassium catalyst has been developed by constructing a well-organized axially chiral ligand composed of one 1,10-phenanthroline unit and two axially chiral 1,1'-bi-2-naphthol (BINOL) units. In the presence of this catalyst, good to excellent yields and enantioselectivities (up to 99 % yield, 98 : 2 er) have been achieved in the ring-opening alcoholytic dynamic kinetic resolution of a variety of biaryl lactams, thereby providing an efficient protocol for catalytic asymmetric synthesis of unnatural axially chiral biaryl δ-amino acid derivatives.

Organocatalytic asymmetric formal [3 + 2] cycloaddition reaction of isocyanoacetates with saccharin-derived 1-azadienes.

An efficient organocatalytic diastereo- and enantioselective formal [3 + 2] cycloaddition reaction of α-isocyanoacetates with saccharin-derived 1-azadienes catalyzed by a dihydroquinine derived squaramide catalyst has been investigated, and it furnished the corresponding directly linked benzo[d]isothiazole 1,1-dioxide-dihydropyrroles with two adjacent tertiary-quaternary stereocenters in high yields (up to 98%), with moderate to excellent stereoselectivities (up to >20 : 1 dr and 97% ee) under mild conditions.

Asymmetric synthesis of dihydrocoumarins via catalytic sequential 1,6-addition/transesterification of α-isocyanoacetates with para-quinone methides.

A catalytic asymmetric synthesis of 3,4-dihydrocoumarins with adjacent tertiary-quaternary stereocenters by 1,6-addition/transesterification cascade reaction of α-isocyanoacetates with ortho-hydroxyphenyl-substituted para-quinone methides (p-QMs) has been developed. Using a combination of dihydroquinidine-derived aminophosphine and silver nitrate as a binary catalytic system, moderate to good yields, excellent diastereoselectivities (>20 : 1 dr) and good to excellent enantioselectivities (up to 94% ee) were achieved for a wide range of isocyanoacetates and p-QMs.

Cinchona Alkaloid Squaramide-Catalyzed Asymmetric Ugi-Type Reaction of Isocyanoacetates with C,N-Cyclic Azomethine Imines: Access to Chiral Oxazole-Substituted Tetrahydroisoquinolines.

We reported herein an unexpected cinchona alkaloid-derived squaramide-catalyzed asymmetric two-component Ugi-type reaction of α-aryl-substituted isocyanoacetates with C,N-cyclic azomethine imines, which provides concise access to optically active C1-oxazole-substituted tetrahydroisoquinolines in good yields (86-93%) and high enantioselectivities (up to 98% enantiomeric excess) under mild conditions.

Organocatalyzed asymmetric tandem conjugate addition-protonation of isocyanoacetates to 2-chloroacrylonitrile.

An efficient organocatalytic asymmetric tandem conjugate addition-protonation of α-substituted isocyanoacetates to 2-chloroacrylonitrile catalyzed by dihydroquinine-derived thiourea has been investigated, affording the corresponding adducts with two non-adjacent tertiary-quaternary stereocenters in excellent yields (up to 99%) along with good to excellent diastereo- and enantioselectivities (up to 20 : 1 dr, up to 95% ee) under mild conditions. The adduct can also be transformed into chiral γ-lactam by synthetic transformations.

Diastereo- and enantioselective Mannich/cyclization cascade reaction of isocyanoacetates with cyclic sulfamide ketimines by cinchona alkaloid squaramide/AgOAc cooperative catalysis.

We have developed an efficient diastereo- and enantioselective Mannich/cyclization cascade reaction of α-substituted isocyanoacetates with 4-aryl-3-carbonyl-1,2,5-thiadiazole-1,1-dioxide type cyclic sulfamide ketimines cooperatively catalyzed by cinchona alkaloid-derived squaramide and AgOAc. The corresponding optically active 2,3,3a,4-tetrahydroimidazo[1,5-b][1,2,5]thiadiazole-1,1-dioxide derivatives were obtained in excellent yields (up to 99%) and good to excellent stereoselectivities (up to >20 : 1 dr, up to 94% ee).

Cinchona Alkaloid Squaramide-Catalyzed Asymmetric Michael Addition of α-Aryl Isocyanoacetates to ß-Trifluoromethylated Enones and Its Applications in the Synthesis of Chiral ß-Trifluoromethylated Pyrrolines.

Cinchona alkaloid squaramide can effectively catalyze the asymmetric Michael addition of α-aryl isocyanoacetates to ß-trifluoromethylated enones, affording the corresponding adducts with an adjacent chiral tertiary carbon center bearing a CF3 group and a quaternary carbon center in moderate to good yields along with excellent stereoselectivities. The adduct can be easily transformed into biologically attractive chiral ß-trifluoromethylated pyrroline carboxylate in high yield via an isocyano group hydrolysis/cyclization/dehydration cascade reaction by treating with acid. The one-pot enantioselective Michael addition/isocyano group hydrolysis/cyclization/dehydration sequential protocol has also been investigated.

Highly active chromium-based selective ethylene tri-/tetramerization catalysts supported by alkenylphosphanyl PNP ligands.

A series of novel diphosphinoamine (PNP) ligands bearing a P-alkenyl group were synthesized and applied in chromium-catalyzed selective ethylene tri-/tetramerization by in situ combination of Cr(acac)3 and modified methylalumoxane (MMAO-3A). The ligand substitution and oligomerization conditions have a remarkable influence on the catalytic activity and controllable selectivity. Most of these PNP ligands are highly active for ethylene tri-/tetramerization with considerable selectivity. An asymmetric diisopropenylphosphanyl ligand with an N-cyclohexyl group achieved the highest activity of 2036 kg (g Cr h-1)-1 with a high total selectivity of 81.1 wt% toward valuable 1-hexene (43.0 wt%) and 1-octene (38.1 wt%) at 40 bar ethylene and 60 °C. An asymmetric mixed isopropenyl/ethylphosphanyl ligand with an N-isopropyl group exhibited a high 1-octene selectivity of 65.5 wt% and a high total 1-hexene/1-octene selectivity (91.5 wt%) with a high activity of 1256 kg (g Cr h-1)-1.

Cinchona alkaloid squaramide catalyzed enantioselective hydrazination/cyclization cascade reaction of α-isocyanoacetates and azodicarboxylates: synthesis of optically active 1,2,4-triazolines.

An efficient enantioselective hydrazination/cyclization cascade reaction of α-substituted isocyanoacetates to azodicarboxylates catalyzed by Cinchona alkaloid derived squaramide catalysts has been investigated, affording the optically active 1,2,4-triazolines in excellent yields (up to 99%) and good to excellent enantioselectivities (up to 97% ee) under mild conditions.

Enantioselective Michael addition of 3-aryloxindoles to a vinyl bisphosphonate ester catalyzed by a cinchona alkaloid derived thiourea catalyst.

A highly enantioselective Michael addition of 3-aryloxindole to vinyl bisphosphonate ester catalyzed by a cinchonidine derived thiourea catalyst has been investigated. The corresponding adducts, containing a chiral quaternary carbon center and geminal bisphosphonate ester fragment at the 3-position of the oxindole, were obtained in moderate to good yields (65-92%) and moderate to good enantioselectivities (up to 92% ee).

[Predicative value of expression of TrkB and TRIM29 in biopsy tissues from preoperative gastroscopy in lymph node metastasis of gastric cancer].

OBJECTIVE: To analyze the expressions of TrkB and TRIM29 in biopsy tissues from preoperative gastroscopy in patients with gastric cancer and investigate the relationship between their expression and rate of lymph node metastasis. METHODS: Through immunohistochemistry, the authors analyzed the expression status of TRIM29 and TrkB in biopsy tissues from preoperative gastroscopy in 67 patients with a diagnosis of gastric cancer undergoing radical operations during 2005 - 2009 at Peking University Third Hospital. There were 39 males and 28 females. Then the relationship was explored between the expression of both proteins and lymph node metastasis and other clinical pathological factors. Image pro Plus 6.0 software was used for image analysis. The data underwent a logarithmic process and were analyzed through SPSS 17.0 statistical software. RESULTS: The expression of TrkB in lymph node metastasis (n = 42) was higher than that in without lymph node metastasis (n = 25) (lgA 4.79 ± 0.42 vs 3.98 ± 0.71, t = -5.873, P = 0.003), while the expression of TRIM29 with lymph node metastasis (n = 36) was also higher than that in without lymph node metastasis (n = 24) (5.21 ± 0.27 vs 5.02 ± 0.37, t = -2.257, P = 0.040). Logistic regression analysis showed that the TrkB expression was an independent predictor for lymph node metastasis. A discriminant was set based on the result (discriminant value = 1.705 × TrkB lgA+ 1.803 × TRIM29 lgA-16.880, cutoff value = 0). This discriminant achieved a prediction accuracy of 80.0% (48/60), a positive likelihood ratio 3.332 and a negative likelihood ratio 0.223. Patients with a high expression of TrkB showed a worse survival rate than those with a low TrkB expression [36.0% (9/25) vs 66.7% (16/24), P = 0.047). Patients with a high TRIM 29 expression showed a worse survival rate than those with a low TRIM29 expression [38.1% (8/21) vs 66.7% (14/21), P = 0.044]. CONCLUSION: The expressions of TrkB and TRIM29 are correlated with lymph node metastasis in gastric cancer, and discriminant based on the expressions of TrkB and TRIM29 had important values for preoperative prediction of lymph node metastasis in gastric cancer.

Synthesis of axially chiral oxazoline-carbene ligands with an N-naphthyl framework and a study of their coordination with AuCl·SMe(2).

Axially chiral oxazoline-carbene ligands with an N-naphthyl framework were successfully prepared, and their coordination behavior with AuCl·SMe(2) was also investigated, affording the corresponding Au(I) complexes in moderate to high yields.

Conformational enantiodiscrimination for asymmetric construction of atropisomers.

Molecular conformations induced by the rotation about single bonds play a crucial role in chemical transformations. Revealing the relationship between the conformations of chiral catalysts and the enantiodiscrimination is a formidable challenge due to the great difficulty in isolating the conformers. Herein, we report a chiral catalytic system composed of an achiral catalytically active unit and an axially chiral 1,1'-bi-2-naphthol (BINOL) unit which are connected via a C-O single bond. The two conformers of the catalyst induced by the rotation about the C-O bond, are determined via single-crystal X-ray diffraction and found to respectively lead to the formation of highly important axially chiral 1,1'-binaphthyl-2,2'-diamine (BINAM) and 2-amino-2'-hydroxy-1,1'-binaphthyl (NOBIN) derivatives in high yields (up to 98%), with excellent enantioselectivities (up to 98:2 e.r.) and opposite absolute configurations. The results highlight the importance of conformational dynamics of chiral catalysts in asymmetric catalysis.

Cu(I)-catalyzed asymmetric chlorination of ß-keto esters in the presence of chiral phosphine-Schiff base type ligands.

Chiral phosphine-Schiff base type ligand L8 prepared from (R)-(-)-2-(diphenylphosphino)-1,1'-binaphthyl-2'-amine was found to be a fairly effective ligand for Cu(I)-promoted enantioselective chlorination of ß-keto esters to give the corresponding products in high yields and with moderate enantioselectivities.

Synthesis of chiral mono(N-heterocyclic carbene) palladium and gold complexes with a 1,1'-biphenyl scaffold and their applications in catalysis.

Axially chiral mono(NHC)-Pd(II) and mono(NHC)-Au(I) complexes with one side shaped 1,1'-biphenyl backbone have been prepared from chiral 6,6'-dimethoxybiphenyl-2,2'-diamine. The complexes were characterized by X-ray crystal structure diffraction. The Pd(II) complex showed good catalytic activities in the Suzuki-Miyaura and Heck-Mizoroki coupling reactions, and the (S)-Au(I) complexes also showed good catalytic activities in the asymmetric intramolecular hydroamination reaction to give the corresponding product in moderate ee.

Asymmetric epoxidation catalyzed by alpha,alpha-dimethylmorpholinone ketone. Methyl group effect on spiro and planar transition states.

Asymmetric epoxidation of olefins by using an alpha,alpha-dimethylmorpholinone-containing chiral ketone catalyst (4) has been investigated. This ketone, which has the combined features of several previously studied catalysts, is an effective catalyst for trans- and trisubstituted olefins, and up to 97% ee has been achieved. The alpha,alpha-dimethyl group has significant impact on spiro and planar transition states.

A diacetate ketone-catalyzed asymmetric epoxidation of olefins.

A fructose-derived diacetate ketone has been shown to be an effective catalyst for asymmetric epoxidation. High ee values have been obtained for a variety of trans and trisubstituted olefins including electron-deficient alpha,beta-unsaturated esters as well as certain cis olefins.

A better prediction of progression-free survival in diffuse large B-cell lymphoma by a prognostic model consisting of baseline TLG and %ΔSUVmax.

In the era of rituximab, the International Prognostic Index (IPI) has been inefficient in initial risk stratification for patients with R-CHOP-treated diffuse large B-cell lymphoma (DLBCL). To estimate the predictive values of PET/CT quantitative parameters and three prognostic models consisting of baseline and interim parameters for three-year progression-free survival (PFS), we conducted an analysis of 85 patients in China with DLBCL underwent baseline and interim PET/CT scans and treated at the Department of Hematology of Peking University Third Hospital from November 2012 to November 2017. The PET/CT parameters, viz. the baseline and interim values of standardized uptake value (SUVmax ), total metabolic tumor volume (TMTV), and total lesion glycolysis (TLG), and their rates of change, were analyzed by a receiver operating characteristics curve, Kaplan-Meier analysis, and log-rank test. Besides, the National Comprehensive Cancer Network International Prognostic Index (NCCN-IPI) was also included in the multivariate Cox hazards model. Owing to the strong correlation between TMTV and TLG at baseline and interim (Pearson's correlation coefficient, r = 0.823, P-value = 0.000, and 0.988, P-value = 0.000, respectively), only TLG was included in the multivariate Cox hazards model, where TLG0  > 1036.61 g and %ΔSUVmax  < 86.02% showed predictive value independently (HR = 10.42, 95% CI 2.35-46.30, P = 0.002, and HR = 4.86, 95% CI 1.27-18.54, P = 0.021, respectively). Replacing TLG in the equation, TMTV0 and TMTV1 both showed significantly predictive abilities like TLG (HR = 8.22, 95% CI 1.86-32.24, P = 0.005, and HR = 2.96, 95% CI 1.16-7.54, P = 0.023, respectively). After dichotomy, NCCN-IPI also gave a significant performance (P = 0.035 and P = 0.010, respectively, in TLG and TMTV models). The baseline variables, that is, TMTV0 , TLG0 and dichotomized NCCN-IPI, and the interim variables TMTV1 and %ΔSUVmax , presented independent prognostic value for PFS. In prognostic model 2 (TLG0  + %ΔSUVmax ), the group with TLG0  > 1036.61 g and %ΔSUVmax  < 86.02% recognized 19 (82.6%) of the relapse or progression events, which showed the best screening ability among three models consisting of baseline and interim PET/CT parameters.

Asymmetric epoxidation of 1,1-disubstituted terminal olefins by chiral dioxirane via a planar-like transition state.

Various 1,1-disubstituted terminal olefins have been investigated for asymmetric epoxidation using chiral ketone catalysts. Up to 88% ee has been achieved with a lactam ketone, and a planar transition state is likely to be a major reaction pathway.