Stéphanie Norsikian

Enantioselective Carbometalation of Cinnamyl Derivatives: New Access to Chiral Disubstituted Cyclopropanes— Configurational Stability of Benzylic Organozinc Halides

Enantioselectiveadditionofan alkyllithiumcompound acrossa doublebond is achieved by the complexation of various primary or secondary organolithium compounds with (−)-sparteine [Eq. (a)]. This synthetic route is effective, simple, and may be useful for the synthesis of chiral disubstituted cyclopropanes.

Enantioselective Carbolithiation of β-Alkylated Styrene

Abstract Stoichiometric or catalytic amounts of (−) sparteine serve as promoter for enantioselective carbolithiation of β-alkylated, non functionalized styrene.

Coupling the Petasis Condensation to an Iron(III) Chloride-Promoted Cascade Provides a Short Synthesis of Relenza Congeners

Iron(III) chloride hexahydrate promotes a cascade of transformations on a Petasis condensation product that sets up the right dihydropyran precursors of valuable Relenza congeners.

Remarkable stereoselectivity in intramolecular Borono-Mannich reactions: synthesis of conduramines.

An unprecedented intramolecular Petasis condensation provides a novel approach to biologically important conduramines. The compounds are produced with an exclusive anti stereoselectivity for the newly created β-amino alcohol motif. The stereochemical outcome of the reaction is opposite to the one usually observed in the intermolecular reaction.

From Enantiopure Hydroxyaldehydes to Complex Heterocyclic Scaffolds: Development of Domino Petasis/Diels–Alder and Cross‐Metathesis/Michael Addition Reactions

One-step assembly of hexahydroisoindole scaffolds by a sequence that combines the Petasis (borono-Mannich) and Diels-Alder reactions is described. The unique selectivity observed experimentally was confirmed by quantum calculations. The current method is applicable to a broad range of substrates, including free sugars, and holds significant potential to efficiently and stereoselectively build new heterocyclic structures. This easy and fast entry to functionalized polycyclic compounds can be pursued by further transformations, for example, additional ring closure by a cross-metathesis/Michael addition domino sequence.

Glycosylation with N -acetyl glycosamine donors using catalytic iron( iii ) triflate: from microwave batch chemistry to a scalable continuous-flow process

Efficient and highly selective glycosylation reactions of peracetylated β-D-N-acetyl gluco- and galactosamine are described using catalytic iron(III) triflate under microwave conditions or in a continuous flow process. Simple β-glycosides and β-(1 → 6), β-(1 → 2) and β-(1 → 3) linked disaccharides bearing various protecting groups were obtained in high yields. Insights into the glycosylation mechanism are discussed.

Useful Sialic Acid Modifications Catalyzed by Palladium

A regio- and stereocontrolled solution for a selective modification at the C-2 or C-4 position of N-acetylneuraminic acid involves the use of allylic substitution catalyzed by palladium. As illustrated in the scheme, regioselective malonylation is under the strict influence of the ligands associated with the allylpalladium complex.

Synthesis of a Tiacumicin B Protected Aglycone

Tiacumicin B is an antibiotic endowed with the remarkable ability to interact with a new biological target, giving it an inestimable potential in the context of the ever-growing and worrisome appearance of resistances of bacteria and mycobacteria to antibiotics. The synthesis of an aglycone of tiacumicin B ready for glycosylation is reported. The key steps of this approach are a [2,3]-Wittig rearrangement, a Pd/Cu-catalyzed allene-alkyne cross-coupling, a E-selective cross-metathesis, and a final ring-size selective macrolactonization.

Chapter 7:Recent results in synthetic glycochemistry with iron salts at Orsay-Gif

This review particularly emphasizes synthetic applications resulting from cascade or one-pot transformations and a glycosylation reaction promoted by ferric salts. These easy to handle, cheap and environment-friendly salts have been examined for their ability to induce, as a Lewis acid, fast carbohydrate-based modifications in our laboratories at Orsay and Gif sur Yvette. A short synthetic route to the dihydropyran framework of anti-influenza constructs is reported by coupling the Petasis three-component condensation to an iron(iii)-promoted one-pot cascade of deprotection – C–C double bond isomerization – cyclization - oxazoline formation. We also show that iron(iii) chloride hexahydrate is most appropriate to catalyze a one-pot regioselective protection of mono- and disaccharides. This iron(iii) catalysis renders multi-step routes, such as chemical oligosaccharide syntheses, faster. In the last section, we report a catalytic glycosylation method particularly simple and straightforward leading to the important β-d-GlcNAc motif, in which the more electrophilic iron(iii) triflate activates the readily available peracetate of N-acetyl-β-d-glucosamine. This glycosylation does not necessarily require the formation of the mandatory oxazolinium intermediate.

Study of the Construction of the Tiacumicin B Aglycone

Our study of the synthesis of the aglycone of tiacumicin B is discussed here. We imagined two possible strategies featuring a main retrosynthetic disconnection between C13 and C14. The first strategy was based on Suzuki-Miyaura cross-coupling of 1,1-dichloro-1-alkenes, but the failure of this pathway led us to use a Pd/Cu-dual-catalyzed cross-coupling of alkynes with allenes that had never been implemented before in a total synthesis context. We used density functional theory calculations to guide our strategic choices concerning a [2.3]-Wittig rearrangement step and the final ring-size selective Yamaguchi macrolactonization. This led to two syntheses of the aglycone of tiacumicin B, with one of last generation delivering ultimately an adequately protected and glycosylation-ready aglycone.