Lachnanthospirone,a dimeric 9-phenylphenalenone from the seeds of Lachnanthestinctoria ell.

The structure of lachnanthospirone [$\text{4}$] a novel dimeric pigment from $\text{Lachnanthes}$$\text{tinctoria}$ has been established from the X-ray crystal structure of a derivative [$\text{3}$] in which the spirolactone present in the natural product has been opened.     

Benzimidazolinetriones. Reactions of 2,5,6- and 2,4,7-benzimidazolinetriones

The condensation of 2,5,6-benzimidazolinetrione with ethylenediamine resulted in the formation of the 1,3-dihydro-2H-imidazo[4,5-g]quinoxalin-2-one ring system. The reaction of this trione with excess ethanethiol resulted in the isolation of three hydroquinones which were oxidized to the respective quinones. 2,4,7-Benzimidazolinetrione was shown to undergo a Diels-Alder reaction with isoprene and a mono-addition reaction with benzenethiol.     

2,3,7-三羟基-9-(3,4-二羟基)苯基荧光酮光度法测定锌

研究了新型苯基荧光酮类显色试剂2,3,7-三羟基-9-(3,4-二羟基)苯基荧光酮(3,4-DHPF)与锌离子显色反应的条件及应用. 结果表明, 在阳离子表面活性剂溴化十六烷基三甲胺(CTMAB)存在下, 在pH 8.2的Na2HPO4-KH2PO4缓冲溶液中, 锌与3,4-DHPF形成1∶1的红色络合物, 所形成的络合物的最大吸收值位于560 nm处, 表观摩尔吸光系数为1.23×105 L·mol-1·cm-1;红色络合物至少稳定8 h以上, 锌含量在0～1.40 μg/5 mL范围内符合比尔定律;拟定方法已用于茶叶中微量锌的测定.     

Biosynthesis of the cytochalasans. Part III. C-NMR. of cytochalasin B (phomin) and cytochalasin D. Incorporation of [1-13C]- and [2-13C]-sodium acetate

Sequential single frequency decoupling and partially relaxed Fourier transform (PRFT) are used to assign the natural abundance ¹³C-NMR. spectra of cytochalasin B (phomin) ( 1 ) and cytochalasin D ( 2 ). Cultures of Phoma spec. S 298 were fed [2-¹³C]-sodium acetate, and the distribution of this precursor in cytochalasin B (phomin) ( 1 ) was determined by ¹³C-NMR. spectroscopy. Likewise, the labelling patterns in cytochalasin D (zygosporin A) ( 2 ) from Zygos-posium masonii could be identified after incorporation of [2-¹³C]-sodium acetate and [l-¹³C]-sodium acetate. The results confirm previous proposals for the biogenesis of the cytochalasans from phenylalanine, methionine, and a C₁₈, or C₁₆, polyketide part.     

Evaluation of 13C-phenylalanine and 13C-tyrosine breath tests for the measurement of hepatocyte functional capacity in patients with liver cirrhosis.

Liver disease is associated with an abnormal elevation of the plasma concentrations of the aromatic amino acids phenylalanine and tyrosine. The liver is the main site of aromatic amino acid metabolism, particularly the hydroxylation of phenylalanine to tyrosine and further tyrosine degradation. In the present study, we have examined the usefulness of the L-[1-13C]phenylalanine breath test (13C-PheBT) and L-[13C]tyrosine breath test (13C-TyrBT) for the detection of hepatic damage in patients with liver cirrhosis. First, the time courses of 13CO2 excretion after the administration of L-[1-13C]phenylalanine and L-[1-13C]tyrosine were compared. The peak times (the time expressed in minutes at which 13CO2 excretion was maximal) were 20 min in both breath tests, but 13C-TyrBT gave a higher peak than 13C-PheBT. Next, the parameters of 13C-PheBT and 13C-TyrBT were compared with biochemical liver function test values. These parameters were well correlated with several liver blood test values conventionally regarded as measures of hepatocyte functional reserve. Therefore, 13C-PheBT and 13C-TyrBT may be useful to assess the degree and progression of hepatic dysfunction.     

Carbon-13 NMR data for 1- and 2-naphthyltrimethylstannanes and 9-phenanthryltrimethylstannane

Carbon-13NMR data recorded in the pulsed Fourier transform mode are re- ported for 1- and 2-naphthyltrimethyl- stannanes and 9-phenanthryltrimethyl- stannane. Assignments of ring carbon resonances are based on magnitudes of tin-carbon spin-spin coupling constants, substituent chemical shifts, spin-lattice relaxation times and proton coupled spectra.     

Stereoselective synthesis of C1-C9 and C9-C17 fragments of (+)-13-deoxytedanolide

An efficient and highly stereoselective asymmetric synthesis of C1-C9 and C9-C17 fragments of (+)-13-deoxytedanolide have been achieved. Utilization of desymmetrization technique to prepare the triol with five stereogenic centers, regioselective Sharpless asymmetric dihydroxylation, Evans' aldol reaction, chiral methylation, and Wittig olefination are highlights of the synthesis.     

2, 3, 7-三羟基-9-间羟基苯基荧光酮的合成及其 分析性能的研究

研究合成了新试剂2,3,7-三羟基-9-间羟基苯基荧光酮(简称m-HPF)。测定了试剂各级酸离解常数。研究了试剂的化学发光性能和试剂与金属离子的显色行为。结果表明,只有Co^2^+离子对m-HPF-H~2O~2体系有较强的催化发光作用;在表面活性剂存在下,试剂与许多离子都呈灵敏的显色反应。用Huckel分子轨道法(HMO)计算了中性分子及各离子构式的π电子分布,对离解常数进行了归属。     

Incorporation of nonmethyl branches by isoprenoid-like logic: multiple beta-alkylation events in the biosynthesis of myxovirescin A1

Several polyketide secondary metabolites are predicted to undergo isoprenoid-like beta-alkylations during biosynthesis. One such secondary metabolite is myxovirescin A1, produced by Myxococcus xanthus. Myxovirescin is of special interest in that it appears to undergo two distinct beta-alkylations. Additionally, the myxovirescin biosynthetic gene cluster lacks tandem thiolation domains required in the synthesis of other beta-branched secondary metabolites. To probe the origins of the beta-branches in myxovirescin, we heterologously overexpressed the proteins predicted to be responsible for myxovirescin beta-alkylation and reconstituted their activities in vitro on model substrates. Our results confirm that myxovirescin undergoes two isoprenoid-like beta-alkylations during its biosynthesis, including an unprecedented beta-ethylation. The study of its biosynthesis should shed light on the scope and requirements for isoprenoid-like biosynthetic logic in a polyketide context.     

2,3,7-三羟基-9-(2,4-二羟基)苯基荧光酮荧光猝灭法测定锰(Ⅱ)

在pH=9.33的NH3.H2O-NH4Cl缓冲介质中,于表面活性剂溴化十六烷基三甲铵(CTMAB)存在下,利用Mn(Ⅱ)与2,3,7-三羟基-9-(2,4-二羟基)苯基荧光酮(DHPF)形成Mn(Ⅱ)-DHPF-CTMAB三元配合物可产生荧光猝灭,建立了荧光猝灭法测定痕量Mn(Ⅱ)的新方法。该体系激发波长λex=520nm,发射波长λem=540nm,荧光猝灭值与Mn(Ⅱ)的含量在0～0.36μg/25mL范围内呈线性关系,检出限为0.02μg/25mL,在CTMAB存在下,配合物摩尔比Mn(Ⅱ)∶DHPF=1∶2。拟定方法用于测定尿样中微量锰的含量,结果满意。     

Reduction of 1-Deoxy -13–oxotaxanes

Numerous reports have described the semisynthesis of paclitaxel and its anologues from different taxoids 1. However, to the best of our knowledge almost all taxoids have a C-1-hydroxyl. Heretofore, the semisynthesis from taxinine, an abundant natural taxoid lacking of C-1-hydroxyl, has only reached the point of C-13 ketone intermediate 2. We have also encountered difficulties in reducing C-13 ketone to corresponding α- hydroxy group using the same conditions as in total synthesis of paclita…     

The Synthesis of 13C9-15N-Labeled 3,5-Diiodothyronine and Thyroxine

Thyroid hormones undergo extensive metabolism to regulate hormone activity. A labeled thyroid hormone would be useful to track hormone metabolism through various pathways. While radiolabeled thyroid hormones have been synthesized and used for in vivo studies, a stable isotope labeled form of thyroid hormone is required for studying thyroid hormone metabolism by LC-MS/MS, an analytical technique that has certain advantages without the complications of radioactivity. Here we report the synthesis of ¹³C₉-¹⁵N-T₂ and ¹³C₉-¹⁵N-T₄, two labeled thyroid hormone derivatives suitable for in vivo LC-MS/MS studies.

Supplemental materials are available for this article. Go to the publisher's online edition of Synthetic Communications® to view the free supplemental file.     

The mass spectrum of 1-(2-thienyl) hexane-1-13C

The mass spectrum of 1-(2-thienyl) hexane-1-¹³C is reported. The principal fragmentation routes ofthe parent ion are delineated. Beta cleavage of the alkyl chain predominates, and the label retention indicates that the alpha carbon atom remains with the charged ring moiety. A substantial part of the m/e 97 ion undergoes a ring expansion to a six membered ring. A small amount of alpha cleavage of the alkyl chain occurs with the expected loss of the label. Further fragmentation of the ions from initial alpha or beta cleavage produces similar fragment ions. It is noted that many of the neutral particles lost in the formation of the fragment ions are typical of those encountered in the alkylbenzenes or other aromatic ion systems.     

7-Deazapurine biosynthesis: NMR study of toyocamycin biosynthesis in Streptomyces rimosus using 2-13C-7-15N-adenine

Although 7-deazapurines are well known and feature in the hypermodified RNA base queuosine, and in a range of nucleoside antibiotics such as toyocamycin, a mechanistic understanding of their biosynthesis is a longstanding problem. In particular, the obligatory loss of the N-7 nitrogen atom is puzzling, and in order to address this mechanistic conundrum a novel doubly labeled purine, [2-(13)C, 7-(15)N]-adenine, has been prepared and used as a biosynthetic precursor to toyocamycin in Streptomyces rimosus. NMR spectroscopy and mass spectrometry clearly showed incorporation of (13)C but loss of (15)N in the toyocamycin produced.     

Purinenucleoside analogs. 2. 9-(1-Alkoxyethyl-1)-6-substituted purines

Vinyl ethers react with 6-chloro- and 6-methylthiopurines in acid medium to give 9-(1-alkoxyethyl-1)-6-chloro- and 6-methylthiopurines. The 6-chloro compounds were used to prepare 9-(1-alkoxyethyl-1)-6-mercaptopurines. All the synthesized compounds proved to be inactive against lympholeucosis P 388, and Lewis carcinona grafted under kidney capsules in mice.For Communication 1, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 403–406, March, 1986.     

Oxidation products of arachidonic acid I. The synthesis of methyl 8R, 11R, 15-trihydroxy-9S, 12-oxyeicosa-5Z, 13E-dienoate (19)

Diacetone glucose was converted in high yield to 3-deoxy-5-6-anhydro-1,2-0-isopropylidene-D-glucofuranose($\text{3}$), which was transformed to title compound.³ Its mass spectrum confirms the structure of a naturally occurring oxidation product of arachidonic acid first described by wolfe and Pace-Asciak.⁴