Selective reduction of aromatic azides in solution/solid-phase and resin cleavage by employing BF3·OEt2/EtSH. Preparation of DC-81

An efficient method for the reduction of aromatic azides in both solution and solid-phase has been developed by employing BF₃·OEt₂/EtSH. This report also describes resin cleavage employing this reagent system. Further, this protocol has been utilized for the solution as well as the solid-phase synthesis of pyrrolo[2,1-c][1,4]benzodiazepines, including the naturally occurring antibiotic DC-81 and fused [2,1-b]quinazolinones.     

An efficient solid-phase synthesis of biologically important DNA-interactive pyrrolo[2,1-c][1,4]benzodiazepine dimers (DSB-120) and their C2-fluorinated analogues

A facile method for the solid-phase synthesis of pyrrolo[2,1-c][1,4]benzodiazepine dimers has been developed. p-Nitrophenyl carbonate Wang resin attached to 2-amino-5-methoxy-methyl benzoate has been utilized as the resin-bound starting material and these reactions are monitored by FT-IR spectroscopy of resin beads.     

The Role of Sulphonamides and N-Sulphonyl Ketimines/Aldimines as Directing Groups in the Field of C−H Activation

Sulphonamides and N-sulphonyl ketimines/aldimines have turned out to be versatile motifs in the field of synthetic and medicinal chemistry. The field of C−H activation/functionalization flourished remarkably due to their synthetic applicability and directing group plays a remarkable role to achieve regioselectivity in these reactions. The current review summarizes recent tactics by utilizing sulphonamides and N-sulphonyl ketimines/aldimines as directing groups for C−H activation or functionalization. As a directing group, they also facilitate site selectivity and late-stage functionalization of drug molecules in order to construct complex scaffolds of therapeutic importance by C−H activation.     

Separation and determination of diastereomers of lambda-cyhalothrin by normal phase-liquid chromatography using a CN column.

A simple and rapid normal-phase liquid-chromatographic method for the separation and determination of diastereomers of lambda-cyhalothrin using a CN column and detection at UV-230 nm has been developed. This method has the advantage of totally resolving each of the diastereomers from impurities, such as meta-phenoxy benzaldehyde, cyhalothric acid and cyhalothric acid chloride, of technical and formulated materials, allowing one to monitor the low-temperature conversion of diastereomers of lambda-cyhalothrin for process development.     

Synthesis and Antimicrobial Evaluation of Bis-3,5-disubstituted Isoxazoles Based Chalcones

A series of bis-isoxazoles blended chalcones 7a–7j are synthesized in high yields. The combination of three pharmacologically active moieties in a single scaffold results in the synergistic effect in their bioactivity. All the newly synthesized compounds are characterized by IR, NMR and Mass spectroscopy. The target compounds 7a–7j are assessed for their antimicrobial activity and these demonstrate high to excellent activity against tested bacterial and fungal strains. The products 7f, 7h, 7j, and 7i demonstrate potent antimicrobial activity at concentrations 75 and 100 μg/mL.

     

Enantioselective total synthesis of (S)-(−)-quinolactacin B

The enantioselective total synthesis of (−)-quinolactacin B (−)-1 was performed in seven steps and 33% overall yield from tryptamine. The synthesis features the use of ruthenium catalytic asymmetric hydrogen reaction to introduce the chirality in dihydro-β-carboline 2. Based on Noyori’s work, the hydrogenation using the (R,R)-TsDPEN-Ru complex produces dihydro-β-carbolines possessing the (S) absolute configuration, the corrected asymmetric center of the natural product. The synthetic quinolactacin B displayed optical rotations that was in accordance with that of the natural product, thereby supporting the (S) configuration for natural quinolactacin B. The final product’s stereochemical assignment is in agreement with that proposed by Nakagawa and co-workers.     

Synthesis of C8-C8/C2-C8-linked triazolo pyrrolobenzodiazepine dimers by employing ‘click’ chemistry and their DNA-binding affinity

A series of 1,2,3-triazole-containing pyrrolo[2,1-c][1,4]benzodiazepine dimers have been prepared efficiently by employing a ‘click’ chemistry protocol. This method involves 1,3-dipolar cycloaddition of terminal alkynes with organic azides using a Cu(I)-catalyst. Further, these molecules exhibited interesting DNA-binding affinity profiles.     

Synthetic Studies Toward (+)‐Spongidepsin

A convergent enantiomerically controlled synthetic effort toward (+)‐spongidepsin is reported. The synthesis benefits from the use of readily available and inexpensive starting materials like D ‐mannitol and (?)‐β‐citronellene. Key transformations include Evans asymmetric methylation, Mitsunobu esterification, (1H‐benzotriazol‐1‐yloxy)tripyrrolidinophosphonium hexafluorophosphate (PyBOP)‐mediated amide formation for the preparation of a fully functionalized acyclic precursor, and ring‐closing metathesis (RCM).     

Stereoselective Synthesis of (−)‐Pinidinone

A simple and efficient stereoselective linear approach to the total synthesis of (?)‐pinidinone has been accomplished starting from propane‐1,3‐diol, and employing Maruoka asymmetric allylation and Grubbs' olefin cross‐metathesis as the key steps.