A Convenient Multigram Synthesis of DABSO Using Sodium Sulfite as SO₂ Source

A convenient synthesis of DABCO·(SO₂)₂ (abbreviated as DABSO) is reported. Using a two-chamber setup, sulfur dioxide is generated in one chamber and consumed in the other. This closed system overcomes safety issues related to working with toxic SO₂ gas. Pressure build-up is avoided by gradually generating the gas using sodium sulfite as precursor. Moreover, only near-stoichiometric amounts of SO₂ are required for this protocol. The use of anhydrous solvents is not necessary, and every step is performed at room temperature. A scale-up was carried out on a 10 g scale which, after overnight drying, resulted in a quantitative yield

Scaffold Hopping <i>via</i> a Transannular Rearrangement–Encompassing Cascade

A novel reaction cascade for converting benzodiazepinediones into oxazoloquinolinones using carboxylic acid anhydrides in the presence of base has been developed using flow methods. Products are obtained in yields up to 98%

Synthetic Protocol toward Fused Pyrazolone Derivatives via a Michael Addition and Reductive Ring Closing Strategy

A new class of pyrazolo­[3,4-<i>c</i>]­pyridine-3,7-dione and pyrazolo­[3,4-<i>d</i>]­azepine-3,7-dione scaffolds was synthesized via a Michael addition and reductive cyclization strategy. These fused heterocycles were accessed from simple starting materials such as nitroolefins and 3-ethoxycarbonyl­(methylene)­pyrazoline-5-one. The pyrazolo-fused heterocycles were obtained in good overall yields

<i>Ex Situ</i> Generation of Sulfuryl Fluoride for the Synthesis of Aryl Fluorosulfates

A convenient transformation of phenols into the corresponding aryl fluorosulfates is presented: the first protocol to completely circumvent direct handling of gaseous sulfuryl fluoride (SO₂F₂). The proposed method employs 1,1′-sulfonyldiimidazole as a precursor to generate near-stoichiometric amounts of SO₂F₂ gas using a two-chamber reactor. With NMR studies, it was shown that this <i>ex situ</i> gas evolution is extremely rapid, and a variety of phenols and hydroxylated heteroarenes were fluorosulfated in good to excellent yields

Total Synthesis of Septocylindrin B and C-Terminus Modified Analogues

<div><p>The total synthesis is reported of the peptaibol Septocylindrin B which is related to the well documented channel forming peptaibol antibiotic Alamethicin. Several analogues were synthesized with a modified <em>C</em>-terminus, to investigate the SAR of the terminal residue Phaol. All these peptides were tested for their membrane perturbation properties by fluorescent dye leakage assay and for their antibacterial activity.</p> </div

Synthetic strategy for the synthesis of ABCD-ethanolamine with Z = Cbz.

<p>(i) Cbz-removal with H₂, Pd-C and MeOH followed by coupling via EDC/HOAt. (ii) O<i>t</i>Bu-removal with ZnBr₂ .iii) O<i>t</i>Bu-removal of the <i>C</i>-component with TFA/CH₂Cl₂ and Cbz-removal of the <i>N</i>-component with H₂, Pd-C and MeOH, followed by the coupling via EDC/HOAt. (iv) Cbz-removal with H₂, Pd-C and MeOH followed by coupling via PyBOP, followed by deprotection using TBAF.</p

Release of CF from PC∶Ch (7∶3) liposomes after 20 minutes at different ratios R-1 = [peptide]/[lipid].

<p>Alamethicin F50 is used as a reference.</p

Synthetic strategy for the synthesis of Septocylindrin B with Z = Cbz.

<p>(i) Cbz-removal with H₂, Pd-C and MeOH followed by coupling via EDC/HOAt. (ii) O<i>t</i>Bu-removal of the <i>C</i>-component with TFA/CH₂Cl₂ and Cbz-removal of the <i>N</i>-component with H₂, Pd-C and MeOH, followed by coupling using EDC/HOAt. (iii) O<i>t</i>Bu-removal using ZnBr₂ or TFA and Cbz-removal of the <i>N</i>-component with H₂, Pd-C and MeOH, followed by coupling using EDC/HOAt, after which the peptide is Boc deprotected using ZnBr₂. (iv) aminolysis.</p

Synthetic approach for Septocylindrin B.

<p>A' = residue 2–5, A = residue 1–5, B = 6–13, C = residue 14–17, D = residue 18–20.</p

Synthetic strategy for the synthesis of ABCD-Phaol-N6 with Z = Cbz.

<p>(i) Cbz-removal with H₂, Pd-C and MeOH followed by coupling via EDC/HOAt. (ii) O<i>t</i>Bu-removal of the <i>C</i>-component with TFA/CH₂Cl₂ and Cbz-removal of the <i>N</i>-component with H₂, Pd-C and MeOH, followed by coupling using EDC/HOAt. (iii) O<i>t</i>Bu removal using ZnBr₂ (iv) Cbz-removal of the <i>N</i>-component with H₂, Pd-C and MeOH, followed by coupling via HOAt/EDC (v) Boc-deprotection using BiCl₃.</p