Giuseppe Marazzi

A GENERAL, 1+4 APPROACH TO THE SYNTHESIS OF 3(5)-SUBSTITUTED PYRAZOLES FROM ALDEHYDES

Abstract A new, one-pot preparation of 3(5)-substituted-1H-pyrazole is described that employs Horner-Emmons reaction of aldehydes with dianion of novel phosphonate 1 and proceeds through cyclization of N-sodium salt of α,β-unsaturated tosylhydrazones 2 .

N-Sulfonylamidines. Part IV. Intramolecular cyclization of N-Sulfonylamidines of 2-oxoacids: a new synthesis of 3-aminoisothiazole S,S-dioxides.

Abstract N-alkylsulfonylamidines of α-ketoacids 3 bearing both a carbonyl group and at least one H-atom near to the SO 2 group give easily an intramolecular ring-closure rection by action of potassium t-butoxide producing the 3-amino-4,5-dihydro-4-hydroxy-isothiazole S,S-dioxides 4 . Compounds 4 are transformed by thionyl chloride into the corresponding chloro-derivatives 5 which in turn are dehydrochlorinated by potassium carbonate to substituted 3-amino-isothiazole S,S-dioxides 6 .

Novel Analogues of Istaroxime, a Potent Inhibitor of Na+,K+-ATPase: Synthesis and Structure−Activity Relationship†

We report the synthesis and biological properties of novel inhibitors of the Na(+),K(+)-ATPase as positive inotropic compounds. Following our previously described model from which Istaroxime was generated, the 5alpha,14alpha-androstane skeleton was used as a scaffold to study the space around the basic chain of our lead compound. Some compounds demonstrated higher potencies than Istaroxime on the receptor and the (E)-3-[(R)-3-pyrrolidinyl]oxime derivative, 15, was the most potent; as further confirmation of our model, the E isomers of the oxime are more potent than the Z form. The compounds tested in the guinea pig model induced positive inotropic effects, which are correlated to the in vitro inhibitory potency on the Na(+),K(+)-ATPase. The finding that all tested compounds resulted less proarrhythmogenic than digoxin, a currently clinically used positive inotropic agent, suggests that this could be a feature of the 3-aminoalkyloxime derivative class of 5alpha,14alpha-androstane.

Determination of absolute configuration of the derivative from 2-[4-(1-oxo-2-isoindolinyl)-phenyl]-propionic acid and R-(+)-1-phenylethylamine by 1H-NMR spectroscopy; use of shift reagent with diastereoisomeric amides

The assignment of the S-(+), R-(−) absolute configuration of Indoprofene, an analgesic and anti-inflammatory drug, has been made via an NMR configurational correlation of diastereoisomeric phenylethylamides with the aid of Eu(fod)3.

Identification of impurities in artemisinin, their behavior in high performance liquid chromatography and implications for the quality of derived anti-malarial drugs.

Previous work [1] on the HPLC analysis of artemisinin tentatively identified the two impurities present above trace levels. This identification was based on LC-MS results and NMR of impurities isolated from artemisinin. In this work the impurities have been synthesized allowing verification of their identity by LC-MS. It is found that the previously suggested elution order is incorrect. A determination of relative response factors strongly impacts suggested limits on impurity levels and explains the erroneous peak assignment. The fates of the identified impurities are explored in the transformation of artemisinin to its derivative active pharmaceutical ingredients. A survey of a wide variety of artemisinin samples isolated from different geographical regions, different growing seasons, different plant backgrounds and using different extraction and purification approaches showed that artemisinin has sufficient purity for its intended use as a raw material for anti-malarial drug products.

Novel analogues of Istaroxime, a potent inhibitor of Na+,K+-ATPase: Synthesis, structure–activity relationship and 3D-quantitative structure–activity relationship of derivatives at position 6 on the androstane scaffold

We report the synthesis and biological properties of novel analogues of Istaroxime acting as positive inotropic compounds through the inhibition of the Na(+),K(+)-ATPase. We explored the chemical space around the position 6 of the steroidal scaffold by changing the functional groups at that position and maintaining a basic oximic chain in position 3. Some compounds showed inhibitory potencies of the Na(+),K(+)-ATPase higher than Istaroxime and many of the compounds tested in vivo were safer than digoxin, the classic digitalis compound currently used for the treatment of congestive heart failure as inotropic agent. The 3D-QSAR analyses using comparative molecular field analysis (CoMFA) and comparative molecular similarity indices analysis (CoMSIA) methods have been successfully applied to a set of 63 androstane derivatives as Na(+),K(+)-ATPase inhibitors. The contour plots provide many useful insights into relationships between structural features and inhibitory potency.

Directed resolution of 2-fluoro-2-methylhexanoic acid

Abstract The applicability of Helmchens methods for the separation and determination of absolute configuration of enantiomers via diastereoisomeric phenylethylamides has been tested with 2-fluoro-and 2-methylhexanoic acids, then successfully applied to 2-fluoro-2-methylhexanoic acid.

Digitalis-like compounds: Synthesis and biological evaluation of seco-D and D-homo derivatives

The synthesis of seco-D and D-homo digitalis derivatives, from the carda-14,20(22)-dienolide 1, is described. Selective ozonolysis gave the seco-D 14-ketoaldehyde 2a. Modification of the two carbonyl groups and of the alpha, beta-unsaturated lactone ring of the seco-D 14-ketoaldehyde 2a allowed preparation of derivatives with a broad range of binding affinity to the Na+, K(+)-ATPase receptor. Some of the seco-D derivatives (10, 11b, and 13b) showed a binding affinity similar to that of digitoxigenin, demonstrating that the D-ring is not essential for recognition by the digitalis receptor. In the class of D-homo derivatives the highest binding value, about 15 times lower than that of digitoxigenin, was that of the C/D cis compound 29b; the C/D trans analog 28b showed a 7-fold decrease in binding affinity, indicating that the C/D configuration plays an important role in D-homo derivatives as in the classical digitalis compounds.

Synthesis and biological evaluation of 2-Hydroxy derivatives of digitoxigenin and 3-Epidigitoxigenin

The four stereoisomers of the 2-hydroxy derivatives of digitoxigenin and 3-epidigitoxigenin have been synthesized, their structures established by NMR, and their binding affinity for the digitalis receptor on Na+, K(+)-ATPase evaluated. These derivatives showed lower affinities than the parent compounds. The hydrophilic hydroxy groups in the alpha position are more detrimental to the affinity than hydroxy groups in the beta position.

New digitalis steroids. Synthesis of 17α-amino 5β,14β-steroids by thermolysis of 17β-azidocarbonyloxymethyl derivatives

An efficient procedure for the synthesis of otherwise difficult to access 17α-amino derivatives of the digitalis series is described. The key reaction is the stereospecific thermocyclisation of 3β-acetoxy-l7β-azidocarbonyloxymethyl-5β-androstan-14β-ol 3b to (17R)-3β-acetixy-14β-hydroxyspiro[5β-androstane-17,4′-oxazolidin]-2′-one 4.