Catalytic Asymmetric β-Oxygen Elimination

A catalytic enantioselective β-O-elimination reaction is reported in the form of a zirconium-catalyzed asymmetric opening of meso-ketene acetals. Furthermore, a regiodivergent β-O-elimination is demonstrated. The reaction proceeds under mild conditions, at low catalyst loadings, and produces chiral monoprotected 1,2-diol building blocks in good yield and enantiomeric excess. The combination with a Mitsunobu reaction then gives access to all 1,2-diol stereoisomers and trans-1,2-aminoalcohols in high enantiomeric purity. A stereochemical analysis supported by DFT calculations reveals that a high selectivity in the hydrozirconation step is also important for achieving high enantioselectivity, although it does not constitute the asymmetric step. This insight is crucial for the future development of related asymmetric β-elimination reactions.

Recent advances in the synthesis of 5'-deoxynucleoside phosphonate analogs

: The present review focuses on the synthesis of cyclic 5-deoxynucleoside phosphonate analogs. The formation of various phosphonate alkyl moieties is accomplished through (i) Wittig (or HWE) type condensation to the nucleoside aldehyde moiety; (ii) nucleophilic displacement reaction using phosphonate anion or Lewis acid; (iii) Arbuzov reaction; (iv) olefin cross-metathesis between vinyl phosphonates and vinylated nucleosides; and (v) radical reaction and Pd catalyzed alkyne. For the coupling of nucleobases with cyclic moieties, the Mitsunobu reaction, and Sonogashira-type cross-coupling are usually applied. For the coupling of furanose moieties with nucleobases, Vorbrüggen-type condensation is generally applied. Addition reactions mediated by selenium ions are mainly applied for the coupling of carbocyclic moieties. Their biological activity results are summarized.

Synthesis of (–)-Kopsifoline A and (+)-Kopsifoline E

We report the first total synthesis of (–)-kopsifoline A and (+)-kopsifoline E. Our synthetic strategy features a biogenetically inspired regioselective C17-functionalization of a versatile intermediate containing the pentacyclic core of aspidosperma alkaloids. While this advance intermediate provides (–)-kopsifoline D via C3–C21 bond formation, regioselective C17-boronation of its indoline substructure prior to introduction of the F-ring enables access to (–)-kopsifoline A and (+)-kopsifoline E. The vinylogous urethane substructure of the key intermediate was critical in C17-boronation over a competing C7-boronation in related indole derived substrates. After oxidation of the C17–B bond to introduce the C17-ether, the C3–C21 bond of the targets is secured under the Mitsunobu reaction conditions with the vinylogous urethane as the nucleophilic component.

Convenient Preparation and Spectroscopic Characterization of 7R-Hydroxymatairesinol

The preparation of 7R-HMR (allo-hydroxymatairesinol) is reported by: (a) NaBH4 kinetic reduction of 7R/7S diastereomeric mixture; and (b) epimerization of the C7 hydroxyl group by Mitsunobu reaction and subsequent ester hydrolysis. The availability of highly pure target compound (7R-HMR) made it possible to confirm the structure of the target compound and to complete the full spectroscopic characterization.

Stereoselective Synthesis of Selenium-Containing Glycoconjugates via the Mitsunobu Reaction

A simple and efficient route for the synthesis of new glycoconjugates has been developed. The approach acts as a model for a mini-library of compounds with a deoxy-selenosugar core joined to a polyphenolic moiety with well-known antioxidant properties. An unexpected stereocontrol detected in the Mitsunobu key reaction led to the most attractive product showing a natural d-configuration. Thus, we were able to obtain the target molecules from the commercially available d-ribose via a shorter and convenient sequence of reactions.

Straightforward N-alkylation of diketopyrrolopyrroles through Mitsunobu reaction with benzyl, α-branched, and chiral alcohols

The N-alkylation of diketopyrrolopyrroles (DPPs) represents a fundamental step to ensure solubility and further processability. Commonly used nucleophilic subtitution on halogenated derivatives is replaced in this work by Mitsunobu reaction...