Integration of Nine Steps into One Membrane Reactor To Produce Synthesis Gases for Ammonia and Liquid Fuel

The synthesis of ammonia and liquid fuel are two important chemical processes in which most of the energy is consumed in the production of H₂/N₂ and H₂/CO synthesis gases from natural gas (methane). Here, we report a membrane reactor with a mixed ionic‐electronic conducting membrane, in which the nine steps for the production of the two types of synthesis gases are shortened to one step by using water, air, and methane as feeds. In the membrane reactor, there is no direct CO₂ emission and no CO or H₂S present in the ammonia synthesis gas. The energy consumption for the production of the two synthesis gases can be reduced by 63 % by using this membrane reactor. This promising membrane reactor process has been successfully demonstrated by experiment.     

Total synthesis of the marine alkaloid halitulin

The structure of the strongly cytotoxic marine alkaloid halitulin (1) has been confirmed by total synthesis and its absolute configuration determined as (15S). The synthesis follows a strategy previously reported by one of us and uses an efficient preparation of the quinoline-7,8-diol unit by modified Baeyer-Villiger and Skraup reactions. The O-benzyl protecting groups were removed in the last step of the synthesis by transfer hydrogenolysis without concomitant reduction of the quinoline ring. The method can be applied for the synthesis of halitulin analogues.     

Studies directed toward the first total synthesis of acremodiol and acremonol

Studies directed toward the synthesis of acremodiol and acremonol resulted in the synthesis of two macrodiolides 1, 1a, and 2 besides 3. The attempted synthesis of 1 and 2 confirmed that the absolute stereochemistry defined in the earlier report is incorrect. Compound 1 was synthesized by RCM-mediated macrocyclization. Attempted synthesis of 2 failed to give good yields in the cyclization, and 1a and 2 were synthesized by the Yamaguchi macrolactonization method.     

Directed Metalation?Cross‐Coupling Strategies. Total Syntheses of the Alleged and the Revised Phenanthrene Natural Product Gymnopusin

The total synthesis of gymnopusin ( 2 ) is described. The originally assigned structure for gymnopusin 1a was found to be incorrect by total synthesis using the Directed ortho‐Metalation (DoM)? Cross‐Coupling? Directed remote Metalation (DreM) sequence, a demonstrable key strategy for the regioselective construction of the 9‐phenanthrol core. The revised structure of gymnopusin ( 2 ) was confirmed by synthesis by adopting the same strategy but involving a key remote anionic Fries‐rearrangement step. Both routes highlight methodologies and concepts which may be of value in the regiocontrolled synthesis of phenanthrenoids specifically and in complex polycyclic aromatics in general.     

以一种新型Gemini表面活性剂作为介孔模板剂通过转晶过程合成介孔ZSM-5分子筛

将一种新型Gemini表面活性剂,丙撑基双(十八烷基二甲基氯化铵)[C18H37(CH3)2–N+–(CH2)3–N+–(CH3)2C18H37]Cl2(C18-3-18),作为介孔模板剂用于水热法合成介孔ZSM-5分子筛.结果表明,在130 oC低温晶化即可高效合成介孔ZSM-5分子刷.C18-3-18的加入量可影响到所合成介孔ZSM-5分子筛的相对结晶度和织构性质,它的形成遵从一个转晶过程.在合成初期,凝胶中介孔模板剂C18-3-18的使用导向了介孔材料的生成;随后在TPABr的模板作用下,介孔材料慢慢转晶生成具有MFI结构的介孔ZSM-5;然后所合成的介孔ZSM-5晶粒进一步长大并聚集形成块状颗粒,同时产生晶间介孔.C18-3-18作为介孔导向剂不仅可用于合成介孔ZSM-5分子筛,也可用于其它介孔分子筛的合成中.     

On the influence of cholesterol feeding and of a lipogenic diet on the cholesterogenesis in rat liver in vivo

• (1) The existence of a main regulation site(s) of the cholesterol synthesis located after the squalene formation is demonstrated by cholesterol feeding with labelled glucose, acetate, mevalonate as precursors and by measuring the incorporation rates into cholesterol, squalene, ubiquinones, and fatty acids in rat liver in vivo.
• (2) By administration of labelled squalene in vivo it is shown that the isoprenic synthesis is inhibited between squalene and lanosterol but that other regulation site(s) after the lanosterol formation must exist.
• (3) A regulation site of the cholesterogenesis in rat liver located after the squalene synthesis is also shown after a lipogenic diet administered during 5 days. The cholesterol synthesis is thus reduced to about one third of the control rats. Another regulating site controlling the utilization of acetylcoenzyme A for the synthesis of mevalonate is also shown to exist. No indication was obtained for a regulating influence located between mevalonate and squalene.

     

Making Solid‐Phase Peptide Synthesis Greener: A Review of the Literature

To date, the synthesis of peptides is concurrent with the production of enormous amounts of toxic waste. DMF, CH₂Cl₂, and NMP are three of the most toxic organic solvents used in chemical synthesis and are the most common solvents used for peptide synthesis. Additionally, concerns about the hepatotoxicity caused by exposure to DMF and from the toxic and allergenic nature of additives used in peptide synthesis necessitates the need for a green, environmentally friendly, and safer protocol for peptide synthesis. This review summarizes the current literature on green solid‐phase peptide synthesis successes and challenges encountered. The review concludes with suggestions for future research towards a simple and efficient green peptide synthesis protocol.     

Second-generation total synthesis of (−)-diversifolin

A second-generation total synthesis of (−)-diversifolin has been achieved by a more straightforward strategy, involving a highly stereochemistry-dependent 10-membered ring-closing metathesis and a stereoselective dihydroxylation/lactone transposition sequence. Compared to our previous synthesis, the present synthesis is improved in the yield of the key intermediate 2 (20% in 12 steps from diol 8).     

Short,enantioselective, gram-scale synthesis of (−)-zephyranthine

A reasonable synthesis design by strategically integrating functional group manipulation into the ring system construction resulted in a short, enantioselective, gram-scale total synthesis of (−)-zephyranthine. The concise route includes a catalytic Michael/Michael cascade for the asymmetric synthesis of a penta-substituted cyclohexane with three contiguous stereogenic centers, a remarkable 8-step one-pot operation to easily assemble the zephyranthine tetracyclic skeleton, the regioselective construction of a double bond in the C ring and an asymmetric dihydroxylation. This synthesis is also flexible and paves a potential path to a variety of cyclohexylamine-fused tricyclic or polycyclic alkaloids.

A reasonable synthesis design by strategically integrating functional group manipulation into the ring system construction resulted in a short, enantioselective, gram-scale total synthesis of (−)-zephyranthine.     

Total synthesis of PDE-I and -II by copper-mediated double aryl amination

A concise total synthesis of PDE-I and -II featuring copper-mediated double aryl amination with the combination of CuI, CsOAc, and Cs₂CO₃ is described. The highly substituted pyrroloindole skeleton was constructed by a one-pot five-step sequence including double aryl amination, β-elimination, deprotection of a Cbz group, and unexpected formation of an indole via removal of an Ns group followed by rearomatization. The undesired elimination of the protecting group (Ns group) was hampered by using the Boc group as a protecting group in the second-generation synthesis, which excluded the reduction of the indole required in the first-generation synthesis.     

Ultralow concentrations of ibuprofen activate cell prostaglandin synthesis

he interest in the prostaglandin (PG) synthesis by animal cells today grows steadily because of the difficulties in obtaining them by any other way. Murine peritoneal macrophages can under certain con ditions synthesize large amounts of PGs. The effect of well-known nonsteroidal anti-inflammatory drug ibuprofen on PG synthesis by the cells using a high-performance liquid chromatography (HPLC) method with fluorescence detection of 4-bromomethyl-7-methoxy coumarin (BrMMC) derivatives was studied. In our case, the main metabolites were PGE₂ and PGF_2a. The PG synthesis activation effect was shown by ibuprofen concentrations in the 10^-10-10^-14M range with the maximum effect at the 10^-12M. In this case, the ibupro fen effect was comparable in value with the effect of the well-known cell PG synthesis activator—calcium ionophore A₂₃₁₈₇. Although the exact mechanism of such an effect is not clear at the moment, at low concentration, ibuprofen itself is able to activiate PG synthesis in murine peritoneal macrophages.     

Synthesis of dimethyl heterocyclic‐o‐dicarboxylates using dimethyl acetylenedicarboxylate

Dimethyl acetylenedicarboxylate (DMAD) is a very important and useful reagent for the preparation of dimethyl heterocyclic‐o‐dicarboxylates, which are key intermediates in the synthesis of fused pyridazine derivatives. The synthesis of thiopyranes by the Diels‐Alder reaction of dithiocarboxylate derivatives, synthesis of various cyclazines by [2 + 8] cycloaddition reactions, and synthesis of dimethyl pyrazolo[3,4‐b]pyridine‐5,6‐dicarboxylates and polycyclic heterocycles containing the 1,6‐naphthyridine ring system by the reaction of o‐aminonitrile compounds with DMAD are described here.     

A Total Synthesis of Aliskiren

A total synthesis of aliskiren ( 20 ) was accomplished. A key in our synthesis was to use the symmetric trans‐cisoid‐trans‐bis‐lactone 1 as a precursor. It was expediently prepared by three different routes (Scheme 2). Appending the end groups and functional group transformations completed the synthesis (Scheme 3).     

Total synthesis of maremycins A,B, C1/C2, D1, and D2

The total synthesis of maremycins A, B, C₁/C₂, D₁, and D₂ is achieved starting from the natural amino acids l-isoleucine and S-methyl-l-cysteine, in which the total synthesis of maremycins B, C₁/C₂, and D₂ is accomplished for the first time. The synthesis features a position-selective intramolecular bromination process for the synthesis of key chiral building block, a Pd-catalyzed indole synthesis for the preparation of (2S,3S)-β-methyltryptophan and hydroxylation of oxindoles by molecular oxygen. In addition, the protocol for conversion of maremycins A and B to maremycins C and D was improved.     

Fawcettimine‐Type Lycopodium Alkaloids as a Driving Force for Discoveries in Organic Synthesis

Ever since the pioneering synthetic work reported by both Inubushi and Heathcock back in 1980s, the fawcettimine‐type Lycopodium alkaloids have continuously served as a driving force for discoveries in organic synthesis. In this personal account, we summarized our recent synthetic efforts towards the total synthesis of fawcettimine‐type Lycopodium alkaloids, along with a brief summary of relevant syntheses reported by others. Our discussions focus mainly on the key reactions applied during the synthesis of fawcettimine‐type Lycopodium alkaloids.     

Synthesis of N′-substituted Ddz-protected hydrazines and their application in solid phase synthesis of aza-peptides

Hydrazine derivatives are of considerable scientific and industrial value. Substituted hydrazines are precursors for many compounds of great interest and importance, among them aza-peptides. (Aza-peptides are peptide analogues in which one or more of the α-carbons, bearing the side chain residues, has been replaced by a nitrogen atom.) Aza-amino acid residues conserve the pharmacophores necessary for biological activity while inducing conformational changes and increased resistance to proteolytic degradation. These properties make aza-peptides attractive tools for structure-activity relationship studies and drug design. We describe the synthesis of N′-substituted 2-(3,5-dimethoxyphenyl)propan-2-yloxycarbonyl (Ddz) protected hydrazines. A general approach for solid phase synthesis of aza-peptides has been developed based on the in-situ activation of the N-Ddz,N′-substituted hydrazines with phosgene, followed by introduction to the N-terminus of a resin-bound peptide. The Ddz-aza-amino building units include aliphatic, aromatic and functionalized side chains, protected for synthesis by the Fmoc strategy. Solid phase aza-peptide synthesis is demonstrated including selective mild deprotection of Ddz with Mg(ClO₄)₂ and coupling of the next amino acid with triphosgene. Ddz deprotection is orthogonal with the Fmoc and Boc protecting groups, making the solid phase Ddz-aza-peptide synthesis compatible with both the Fmoc and the Boc strategies. The Ddz-protected hydrazines have wide applications in the synthesis of substituted hydrazines and in the synthesis of aza containing peptidomimetics.     

Stibatriptycene

Stibatriptycene (1c) has been synthesized by cyclization of 9-(o-chlorophenyl)-9,10-dihydro-9-stibaanthracene (2c) with an excess of lithium piperidide. The general applicability of this ring closure reaction, first developed for the synthesis of phosphatriptycene (1a) and presumed to proceed by nucleophilic attack of a carbanionic centre on a (slowly generated) benzyne, has further been demonstrated by a new synthesis of the known arsatriptycene (1b) and by the synthesis of stibatriptycene (1c). The structure of 1c was confirmed by IR, ¹H NMR and, in particular, by ¹³C NMR spectroscopy.     

Practical synthesis and applications of benzoboroxoles

A convenient one-pot synthesis of benzoboroxoles has been developed via the reaction of o-bromobenzyl alcohols with NaH, ⁿBuLi, and B(OⁱPr)₃ followed by acidic hydrolysis. Applications of these benzoboroxoles have been demonstrated in Pd-catalyzed cross-coupling reactions and the protocol has been extended for the synthesis of a chiral benzoboroxole. Exceptionally short synthesis of a potent antifungal agent AN2690 and several of its analogs has also been realized.     

Comparison Between Different Syntesis Methods of PMMA/HA Using Ultrasonic Radiation

Summary: The use of PMMA as dental and osseous cement and also in the fabrication of intraocular lenses has been widely reported. The combination of its excellent properties with those of hydroxyapatite (HA) to form a composite material, can result in very interesting properties as a biomaterial. The key is to obtain a good filler dispersion and interface bonding. Ultrasonic radiation seems to be a very versatile method for the synthesis of these materials, since the use of conventional initiators can be avoided, the filler dispersion improved and the interface interaction can be promoted. In the present work PMMA/HA composite materials were prepared by three different synthesis routes using ultrasonic radiation, in order to study the effect of the synthesis method on the final microstructure. Method I : in situ synthesis of PMMA and HA, under ultrasonic radiation by emulsion polymerization of MMA and HA precursors. Method II : in situ synthesis of HA, (from its precursors) by high frequency ultrasound in commercial PMMA solution Method III : in situ polymerization of MMA under high frequency ultrasonic radiation and adding HA to the solution and Method IV Mixing of hydroxyapatite nanocrystals, in different proportions, in a solution of commercial PMMA, by different periods from 10 min to 7 h, under low frequency (conventional) ultrasonic radiation, to compare the effect of high frequency and conventional ultrasound radiation. The different materials were characterized by FTIR, SEM, TEM, DRX, ¹H NMR and TGA. The results showed that, all the composites prepared by in situ synthesis showed an interaction between HA and PMMA, manifested by a bonding of the phosphate groups with the polar groups of the polymer matrix observed by FTIR. On the other hand, when the synthesis was carried out simultaneously adding HA and PMMA precursors a inhibition of the polymerization reaction of MMA was observed.     

A New Base-Labile Anchoring Group for Polymer-Supported Peptide Synthesis

A new base-labile anchoring group, derived from 9-(hydroxymethyl)fluorene-4-carboxylic acid (HO₂CFmoH or HOFmCO₂H; 7), for polymer-supported peptide synthesis os described. The synthesis of 7 starting from 2,2′-biphenyldicarboxylic acid ( 1 ) proceeds in an overall yield of 53%. The group HO₂CFmo exhibits properties similar to the well known Fmoc protecting group: It is stable to acidic conditions and cleavable by 15% piperidine in DMF. In combination with acid labile N^α-protecting groups (e.g. Boc, Ddz, Bpoc, Nps etc.), it renders more flexibility to the stepwise synthesis using polymer supports. The versatility of the new anchoring group in solid- and liquid-phase peptide synthesis is demonstrated for the synthesis of a model peptide.