Ligand creation via linking—a rapid and convenient method for construction of novel supported PyOX-ligands

A novel supported amino alcohol linker was synthesized and utilized for attachment of picolinic acid derivatives onto different supports. When the resin bound molecule was further activated, the PyOX-moiety could be constructed reliably in enantiopure form. Furthermore, an efficient Pd-catalyzed modification of a picolinic acid derivative is presented.     

Synthesis of novel thiol surrogate of Taxol: 2′-deoxy-2′-mercaptopaclitaxel

Paclitaxel analogues with a thiol group in place of the hydroxyl group on the C-13 side chain constitute an interesting avenue of research for the study of new taxoid compounds. A synthetic route for the preparation of the exact thiol surrogate product of Taxol^® by coupling (4S, 5S)-2,4-diphenyloxazoline-5-carboxylic acid with 7-triethylsilyl baccatin III, followed by ring-opening of the oxazoline intermediate with thiolacetic acid is described.     

Synthesis of chiral threefold and sixfold functionalized macrocyclic imidazole peptides

Starting from 4-oxa- or 4-azasubstituted 2-amino-3-oxoesters and (S)-valine, chiral imidazole diamino monocarboxylic acids as well as diamino dicarboxylic acids were prepared in a few synthetic steps. Macrolactamization of the side chain protected imidazole amino acids yields the corresponding 18- and 24-membered ring analogues of the naturally occurring cyclic peptide Westiellamide with various anchoring sites. The threefold functionalized scaffolds 2b-4b and the sixfold functionalized scaffold 5 are versatile central modules for artificial receptors and ligands. Structural investigations of threefold functionalized scaffolds based on oxazole and N-methylimidazole units by DFT modeling are provided.     

Synthesis of the fully functionalized nine-membered diyne core of the C-1027 chromophore

We report the synthesis of the fully functionalized seco-acid of the C-1027 chromophore. The key reaction is a LiN(TMS)₂/CeCl₃-promoted acetylide-aldehyde condensation to construct the highly strained nine-membered diyne. Appropriate functionalization of the substrates significantly affects the yield of the cyclization. The present findings will be the basis of further studies toward the total synthesis of the C-1027 chromophore.     

Synthesis and NMR characterization of a novel crown-ether ring-fused uridine analogue

The chemical synthesis and ¹H NMR analysis of a novel bicyclic uridine derivative, with a 18-crown-6 ether moiety fused at the ribose 2- and 3-positions, as first example of a hitherto unknown class of ribose-modified nucleosides, are here described. NMR-based conformational analysis studies showed for the modified nucleoside a marked preference for an N-type sugar puckering and the nucleobase in the anti conformation, with the uracil favouring the coordination of a sodium ion hosted in the crown ether.     

Enantioselective synthesis of functionalized fluorinated dihydropyrano [2,3-c]pyrazoles catalyzed by a simple hi functional diaminocyclohexane-thiourea

Enantioselective synthesis of functionalized fluorinated dihydropyrano[2,3-c]pyrazoles has been achieved via a diaminocyclohexane-thiourea catalyzed cascade Michael addition and Thorpe-Ziegler type cyclization in high yields （up to 98%） with moderate to good enantioselectivity （up to 90% ee）.     

Synthesis of a novel functionalized tricyclic pyrimidine-fused 1,5-benzodiazepine library

A series of novel tricyclic pyrimidine-fused 1,5-benzodiazepines (PFBZDs) was synthesized using an enaminone-based approach. The key step in the synthetic strategy involves the formation of the CCNMe₂ structure on vicinal carbonyl groups of the 1H-1,5-benzodiazepine-2,4(3H,5H)-dione (BZD). The synthesis of pyrimidine-fused 1,5-benzodiazepines was performed by a simple and efficient method in good to excellent yields under mild and green conditions. The β-enaminoamide intermediates were condensed with thiourea and guanidine derivatives to form the corresponding tricyclic PFBZDs. But reaction of aminoguanidine, thiosemicarbazide, 4-phenylthiosemicarbazide and ethane-1,2-diamine with β-enaminoamides didn't produce any desired product and led to recovery of the corresponding starting BZD.     

Synthesis of novel dihydrooxazine and oxazoline based sugar hybrids from sugar azides

A convenient one-step method for the synthesis of novel dihydrooxazine and oxazoline based sugar hybrids is reported starting from the readily accessible sugar azides and aldehydes. We have used Aubé’s protocol to achieve this transformation. The resulting glycoconjugates could be used to increase the diversity on the sugar backbone and may find applications as potential glycomimetics and in drug discovery.     

A Simple Method for the Synthesis of Unsymmetrical Ureas

A simple one pot procedure for the synthesis of N,N'-unsymmetrical ureas using phenyl chloroformate in THF is described.     

Synthesis and characterization of novel substituted and cyclic benzoquinone derivatives

Novel substituted benzoquinone compounds were synthesized from the reactions of p-chloranil and p-fluoranil with some thiols, amines, and diols in different reaction media. Interesting cyclic compounds like crown ether structures were obtained. The structures of all compounds were characterized by spectroscopic methods and microanalysis.     

Synthesis of functionalized polycyclic compounds via a novel aromatic oxy-Cope rearrangement

Polycyclic compounds have been prepared by aromatic dianionic oxy-Cope rearrangements involving the π bonds of two phenyl rings in a [3,3] sigmatropic rearrangement.     

The simple solvent-free synthesis of 1H-quinazoline-2,4-diones using supercritical carbon dioxide and catalytic amount of base

Only supercritical carbon dioxide (scCO₂) as a reactant and a solvent, and catalytic amount of base (DBU (1,8-diazabicyclo[5.4.0]undec-7-ene), DBN (1,5-diazabicyclo[4.3.0]non-5-ene), Dabco^® (1,4-diazabicyclo[2.2.2]octane), and triethylamine) afforded 1H-quinazoline-2,4-diones in good to excellent yields from 2-aminobenzonitriles. 6,7-Dimethoxy-1H-quinazoline-2,4-dione, which is a key intermediate of medicines (Prazosin, Bunazosin, and Doxazosin) was synthesized successfully in a 97% yield, using 0.1 equiv of DBU under scCO₂ (10 MPa) at 80 °C.     

A novel atom-economic synthesis of functionalized imidazolidines through copper(I)-catalyzed domino three-component coupling and cyclization reactions

An interesting approach to functionalized imidazolidines is described. These compounds are obtained in a copper(I)-catalyzed domino three-component coupling and cyclization reaction involving two formaldehyde-derived imine units and a terminal alkyne. Alternatively, imidazolidines can be obtained from propargylamines and formaldehyde-derived imines. This strategy provides a straightforward and atom-economic pathway to construct imidazolidines with high yields and benefits from readily available starting materials, convenient one-pot operations.     

Density Functional Study of the Reaction Mechanism of Two Oxiimine Alcohol Formations and Their Novel Rearrangements

In this study, the reaction mechanisms of isonitrosoacetophenone (inapH) with ethanolamine (ea) and 1‐phenylethanolamine (pea) have been investigated theoretically using B3LYP/6‐311G(d,p) method to explain why the formation and unexpected rearrangement products occur or not occur. While the reaction between isonitrosoacetophenone (inapH) with ethanolamine gives oximine alcohol ( Ib ), the reaction of 1‐phenylethanolamine with inapH results in the formation of oximine alcohol with a different substituent ( Ia ) and amido alcohol ( IIa ), which is the unexpected rearrangement product. The rearrangement driving forces of compounds from Ia to IIa are calculated as ca. 28 and 23 kJ/mol in the gas and EtOH phases, respectively. These driving forces have been calculated ca. 46 and 45 kJ/mol for the rearrangement of compound Ib to obtain IIb in the same phases, respectively. This high driving force shows that the compound IIb cannot be obtained from rearrangement of compound Ib as described experimentally in the literature. In addition, as the DFT functionals poorly describe dispersion effects, dispersion correction for reaction heat and free‐energy barrier was estimated using the wB97X‐D/6‐311G(d,p). In general, the relative free energies of all molecules calculated from wB97XD method are lower than performed from B3LYP level. The changes of thermodynamic properties for all molecules with temperature ranging from 100 to 500 K have been obtained using the statistical thermodynamic method.     

Thermal immobilization of carboxy functionalized polysiloxanes: Practice and mechanism

Summary The thermal immobilization of polysiloxanes bearing carboxyalkyl functional groups has been investigated. Under conditions of reduced carrier-gas flow, in particular with water vapour saturated, carrier-gas, high degrees of immobilization could be achieved at moderate temperatures (<200°C). The mechanism of immobilization is shown two involve condensation of carboxyl groups of the polysiloxane with silanol groups either originally present in the polymer or formed during the immobilization process. Other polysiloxane stationary phases could also be immobilized under similar conditions when mixed with carboxyalkyl polysiloxanes. In particular, cyanoalkyl silicones which are otherwise difficult to crosslink, are amenable to this form of immobilisation.     

聚噁唑啉的合成及其共混物

综述了唑啉单体的合成及其聚合方法，并对其聚合物的化学改性及共混物作了概述。     

Synthesis of novel substituted naphthoquino[b]-benzo[e][1,4]diazepines via Pictet-Spengler cyclization

Synthesis of novel 4,5-dihydro-1H-1,4-naphthoquino[b]-benzo[e][1,4]diazepine derivatives via Pictet-Spengler cyclization is reported. Reaction of 2,3-diamino-naphthoquinones with aldehydes in the presence of BF₃·Et₂O gives benzodiazepine-naphthoquinones in good yields.     

Synthesis of a novel ethylene-bis(tetrahydroindenyl) ligand containing a functionalized four-carbon tether

In this work we present an efficient synthesis of a novel ethylene-bis(2-methyl-tetrahydroindenyl) ligand, 2b, containing a tethered functional group. The tethered functional group may enable heterogenization of the homogeneous ligand on various solid supports. This strategy is the first attempt of incorporating a functional tether into a bridged metallocene ligand without disrupting the ethane bridge and represents a new approach to heterogenizing metallocene ligands. A practical synthesis was achieved by selective alkylation of the starting material and the Pauson-Khand cyclization. In addition, this strategy offers a new synthetic pathway for the preparation of the ethylene-bis(2-methyl-tetrahydroindenyl) ligand, 1b.     

Synthesis of novel thiol taxoids based on the 7,10-di-(2,2,2-trichloroethyloxycarbonyl)-10-deacetylbaccatin III: both the syn and anti 10-deacetyl-2′-deoxy-2′-mercaptopaclitaxels

Two new kinds of docetaxel compound, with a mercapto group instead of the hydroxyl on the C13 side chain (both syn and anti), via the 7,10-di-(2,2,2-trichloroethyloxycarbonyl)-10-deacetylbaccatin III route, were synthesized. The uses of trans and cis oxazoline compounds, and their stereoselective ring-opening reactions with thiolacetic acid, were proved to be key steps.     

Synthesis of anacardic acids by nucleophilic substitution on 2-aryloxazolines

A new direct synthesis for anacardic acids based in a nucleophilic substitution of a methoxy group in 2-aryloxazolines by long-chained Grignard reagents is reported.