Catalytic regioselective construction of phenylthio- and phenoxyldifluoroalkyl tetrazoles from difluorodiazoketones.

Here we report the design and synthesis of two new difluoro-diazoketone reagents (difluorophenylthiol diazoketone and difluorophenoxyl diazoketone) and their [3+2] cycloaddition reactions with aryldiazonium salts under silver catalysis conditions. This protocol enables regioselective access to a broad scope of difluorophenylthiol- and difluorophenoxyl-substituted tetrazole-carbinols in a one-pot operation. Further synthetic derivatizations including dephenylthiolation and unexpected phenylthiol group migration/fluorination allow the efficient preparation of α-difluoromethyl tetrazole-carbinols and α-trifluoromethyl tetrazole-thioethers.

Remote Fluorination and Fluoroalkyl(thiol)ation Reactions.

Remote functionalization reactions have the power to transform a C-H (or C-C) bond at a distant position from a functional group. This Review summarizes recent advances and key breakthroughs in remote fluorination, trifluoromethylation, difluoromethylation, trifluoromethylthiolation, and fluoroalkenylation reactions. Several powerful strategies have emerged to control the reactivity and distal selectivity such as the undirected radical approach, the 1,5-hydrogen atom transfer, the metal migration, the use of distant directing groups, and the ring-opening reactions. These unconventional and predictable C-H (and C-C) functionalization transformations should allow for the preparation of a wide range of otherwise-difficult-to-access alkyl, aromatic, heteroaromatic, and structurally complex fluorides.

[Status of iron metabolism and erythropoietic proliferation in children with various genotypes of thalassemia].

OBJECTIVE: To study the status of iron metabolism and erythropoietic proliferation in children with various genotypes of thalassemia. METHODS: Serum concentrations of ferritin (SF), transferrin receptor (sTfR) and erythropoietin (EPO) were measured in 158 children with thalassemia. The differences in the concentrations of the three indices among children with different genotypes of thalassemia were compared. The correlations of the hemoglobin level with sereum SF, sTfR and EPO levels were assessed. RESULTS: Among the 158 children with thalassemia, 52(32.9%) were diagnosed with alpha-thalassemia minor, 27(17.1%) with HbH disease, 59(37.4%) with beta-thalassemia minor, 13(8.2%) with beta-thalassemia major, and 7(4.4%) with combining alpha beta thalassemia. The SF levels in children with HbH disease or beta-thalassemia major were significantly higher than those in the other thalassemia groups (P<0.01). The sTfR levels in children with beta-thalassemia major were the highest when compared with those in the other thalassemia groups (P<0.05). The EPO levels in children with beta-thalassemia major were also the highest when compared with those in the other thalassemia groups (P<0.01). There was a negative correlation between hemoglobin and EPO levels in children with HbH disease (r=-0.656, P<0.01) and beta-thalassemia major (r=-0.641; P<0.05). CONCLUSIONS: The status of iron metabolism and erythropoietic proliferation is different in children with different genotypes of thalassemia. A combined measurement of SF, sTfR and EPO may reflect the status of erythropoietic proliferation.

[Studies on the mutation and polymorphism of the TPMT gene in Chinese children with acute leukemia].

OBJECTIVE: To investigate the allelic frequencies and distribution of single-nucleotide polymorphisms within the coding region (cSNPs) of thiopurine S-methyltransferase gene (TPMT) in Chinese children with acute leukemia (AL) and healthy controls, in order to provide genetic references for individual chemotherapy for AL patients by studying the relationship between the cSNP in human TPMT and chemotherapeutic effect of thiopurine drugs. METHODS: The bone marrow samples from 53 children with AL and peripheral blood samples from 115 healthy children were obtained to prepare complementary DNAs (cDNAs). The cDNAs were analyzed for the polymorphisms in the TPMT gene by reverse transcriptase-polymerase chain reaction (RT-PCR)-denaturing gradient gel electrophoresis (DGGE) and DNA sequencing. The distribution of each genotype was evaluated. RESULTS: Two novel heterozygote mutations, 210C>T (C70C, silent) and 622T>C (F208L), were identified in the coding region of the TPMT in a single sample, respectively. The mother of the child with mutation 622T>C was confirmed as the same genotype by DGGE and sequencing (NCBI_ss accession numbers 107796292 and 107795933). Two known polymorphisms, 474T>C (silent) and 719A>G (T240C), were identified. The allelic frequencies were 14.2%, 2.83% and 17.0%, 3.04% in the AL children and control children respectively, with the total allelic frequencies of 16.2% (first reported in the Chinese Han population) and 2.99% respectively. No association with susceptibility to disease was observed. CONCLUSION: Two novel mutations and two known polymorphisms were identified in Chinese children by RT-PCR-DGGE combined with DNA sequencing, which provides the first step to identify genetic markers for predicting variability in response to and toxicity of thiopurine drugs.

[Relationship between glucocorticoid receptors and glucocorticoid resistance in children with idiopathic thrombocytopenia purpura].

OBJECTIVE: To identify the relationship between the expression of alpha and beta-isoforms of glucocorticoid receptors (GR) in peripheral blood mononuclear cells (PBMC) and glucocorticoid resistance in children with idiopathic thrombocytopenia purpura (ITP). METHODS: Real-time PCR was used to detect the expression of GR alpha and GR beta mRNA in PBMC from 30 children with ITP (glucocorticoid-sensitive, n=18; glucocorticoid-resistant, n=12) and 10 healthy children (control group). Enzyme immunoassay was used to measure plasma levels of total glucocorticoids. RESULTS: There were no significant differences in PBMC GR alpha mRNA levels among the glucocorticoid sensitive, the glucocorticoid-resistant and the control groups. Compared with the glucocorticoid-sensitive and the control groups, the expression of GR beta mRNA in the glucocorticoid-resistant group was significantly up-regulated (p<0.01). Plasma total glucocorticoids level in the glucocorticoid-resistant group was found to be much higher than that in the glucocorticoid-sensitive and the control groups (p<0.01). CONCLUSIONS: The up-regulated expression of GR beta mRNA may associated with glucocorticoid resistance in children with ITP.

[Polymorphisms of thymidylate synthase gene detected by RT-PCR-denaturing gradient gel electrophoresis in children with acute leukemia].

OBJECTIVE: Thymidylate synthase (TS) catalyses the conversion of deoxy-uridylate to deoxy-thymidylate and is a key enzyme for DNA synthesis. TS is the target enzyme of 5-fluorouracil (5-FU) and involved in folate metabolism. TS gene polymorphisms play an important role in the efficiency of fluorouracil activity in vivo. This study investigated the allelic frequencies and distribution characters of single-nucleotide polymorphisms within the coding region (cSNPs) of TS gene in Chinese children with acute leukemia (AL) and normal control children in order to explore the possible relationship between the cSNP in human TS gene and chemotherapeutic effects of 5-fluorouracils. METHODS: Bone marrow samples from 53 children with AL and peripheral blood samples from 115 normal children were obtained to prepare complementary DNAs (cDNAs). The cDNAs were analyzed for the polymorphisms in TS gene by reverse transcriptase (RT)-polymerase chain reaction (PCR)-denaturing gradient gel electrophoresis (DGGE) and direct sequencing. The distributive difference of each genotype between AL children and control children was evaluated. RESULTS: A polymorphism 381 A>G (E127E) in the coding region of TS gene was firstly identified in the Chinese population. The 381 A>G allelic frequency in AL children and control children was 12.3% and 13.5% respectively (P>0.05), which were similar to that in the International SNP Bank (12.3%). The allelic frequency of cSNPs was not associated with the susceptibility to AL. CONCLUSIONS: A polymorphism 381 A>G (E127E) in TS gene was successfully identified in children using RT-PCR-DGGE combined with DNA sequencing. There was no significant difference in the allelic frequency of cSNPs in AL children and normal children.

[Study on the relationship between human cytidine deaminase gene polymorphisms and Ara-C sensitivity].

OBJECTIVE: To study the relationship between coding single-nucleotide polymorphisms (cSNPs) in the human cytidine deaminase (CDA) gene and cytosine arabinoside (Ara-C) sensitivity in childhood acute leukemia (AL). METHODS: cDNAs from 87 leukemia and 199 control blood samples were analyzed for the cSNPs in CDA by PCR-denaturing gradient gel electrophoresis (DGGE) and sequencing. Human CDA genes were transformed into E. coli and yeast, respectively. Catalytic activities of the allele CDA and variant CDAs were determined by HPLC assay. The Ara-C sensitivity of the yeast transformants was measured by growth inhibition assays. RESULTS: Three known different polymorphisms, namely, 79A/C (K27Q), 208G/A (A70T) and 435T/C (silent) were identified in the coding region of CDA from an investigated Chinese population and displayed allelic frequencies of 12.1%, 0.5% and 76.2%, respectively. No association with susceptibility to disease was observed. Compared with that of CDA70A, the deamination activities for cytidine and Ara-C substrates of the E. coli transformants carrying human CDA70T were decreased by 53% and 63%, respectively (P<0.01), and the Ara-C IC50 value of the yeast transformants was also significantly decreased by 25% [(973 +/- 61) micromol/L to (735 +/- 31) micromol/L, P<0.05]. CONCLUSIONS: The 3 known cSNPs and their allelic frequencies of CDA are identified in a Chinese childhood AL. The 208A genotype is shown to be more sensitive to Ara-C than 208G genotype.

[Application of PCR-DGGE technique in G-6-PD deficiency].

OBJECTIVE: To detect gene mutations of children with glucose-6-phosphorate dehydrogenase (G-6-PD) deficiency and of carriers of G-6-PD deficiency gene with the technique of polymerase chain reaction and denatured gradient gel electrophoresis (PCR-DGGE), and to explore the value of the technique in the diagnosis of G-6-PD deficiency and G-6-PD deficiency gene carrying. METHODS: cDNAs were harvested by reverse transcription method after RNAs had been extracted from peripheral blood of 43 children with G-6-PD deficiency and of their family members (36 lineages). Electrophoresis behaviors of the fragment from exons 11-12 of G-6-PD cDNA were detected with the technique of PCR-DGGE. Gene sequencing was then performed for the abnormal electrophoresis bands. RESULTS: Abnormal electrophoresis bands were found in the 1304-1520 fragment of G-6-PD cDNA in 33 out of 36 family lineages. The G-6-PD/6-PGD ratio was below 1.00 in 9 mothers of patients. Three of them had the G-6-PD/6-PGD ratio lower than 0.50. The PCR-DGGE bands were the same in the 3 mothers. Gene sequencing showed double heterozygote in the 3 mothers, but the maternal carriers of G-6-PD deficiency gene who had normal G-6-PD/6-PGD ratio showed mono-heterozygote in gene sequencing. Three mutational sites were found in the 1304-1520 fragment, i.e., C1311TG1376T and G1388A. The electrophoresis behaviors were different among the 3 gene mutational sites. CONCLUSIONS: PCR-DGGE is a sensitive and reliable technique in the screening of gene mutations. It is useful in the diagnosis of G-6-PD deficiency, especially in the diagnosis of female G-6-PD deficiency gene carrying.

[Single-nucleotide polymorphisms of the cytidine deaminase gene in childhood with acute leukemia and normal Chinese children].

OBJECTIVE: Cytidine deaminase (CDA) is a key enzyme for metabolizing chemotherapeutic agent cytosine arabinoside (Ara-C), a deoxycytidine analog used for treatment of acute leukemia and lymphomas. Significant variability in the antitumor efficacy and systemic toxicity of Ara-C has been observed in cancer patients. Two missense mutations changing Ara-C sensitivity and toxicity had been found in the human CDA. Coding single-nucleotide polymorphisms (cSNPs) of CDA had been investigated in Japanese, Europeans Africans and Americans, but not in Chinese. The purpose of this study was to survey the allelic frequencies of CDA cSNPs in Chinese children. METHODS: The bone marrow samples from 87 childhood patients with acute leukemia and peripheral blood samples from 199 non-malignancy-bearing children were obtained to prepare complementary DNAs (cDNAs). The cDNAs were analyzed for the polymorphisms in CDA by polymerase chain reaction (PCR)-denaturing gradient gel electrophoresis (DGGE), PCR-restriction fragment length polymorphism (RFLP) and direct-sequencing. The distributive difference of each genotype was evaluated between children with acute leukemia and control children. RESULTS: Three known different polymorphisms, namely, 79A to C (K27Q), 208G to A (A70T) and 435T to C (silent) were identified in the coding region of CDA from the investigated Chinese population and displayed allelic frequencies of 12.1%, 0.52% and 76.2%, respectively. No association with susceptibility to disease was observed. CONCLUSION: This study demonstrates 3 cSNPs and their allelic frequencies of CDA in Chinese children, and provides the first step to identify genetic markers for predicting variability in Ara-C response and toxicity.

[Expression of G-6-PD mRNA in children with G-6-PD deficiency].

OBJECTIVE: To detect the level of glucose-6-phosphate dehydrogenase (G-6-PD) mRNA expression in children with G-6-PD deficiency and their lineal family members in order to explore possible mechanisms of the disease at the transcriptional level. METHODS: RNA was extracted from peripheral blood of 41 children with G-6-PD deficiency and of their lineal family members (29 father lineages and 40 mother lineages). cDNA was then harvested using the reverse transcription method. G-6-PD mRNA expression was detected by quantitative real-time PCR (QRT-PCR). The detection results of G-6-PD mRNA expression in three groups (Patient, Father lineage and Mother lineage) were compared using Statistical Software SPSS 10.0 system. RESULTS: The mean G-6-PD mRNA value in the Patient, Father lineage and Mother lineage groups were 0.57 +/- 0.19, 0.74 +/- 0.21 and 0.67 +/- 0.21 respectively. The G-6-PD mRNA value in the Patient group was significantly lower than both Father lineage (t = -3.18, P < 0.01) and Mother lineage groups (t = -2.54, P < 0.05). CONCLUSIONS: The expression of G-6-PD mRNA decreased in children with G-6-PD deficiency, suggesting that the pathogenesis of this disorder relates to the varying levels of gene transcription.