Synthèse et réactions de didésoxy-5,6-halogéno-6-α-D-xylo-hepténo-5-furannurononitriles. Communication préliminaire

Synthesis and reactions of 5,6-dideoxy-6-halogeno-α-D-xylo-hept-5-eno-furanurononitriles The 5,6-dideoxy-6-chloro-, 6-iodo- and 6-fluoro-3-O-methyl-α-D -xylo-hept-5-eno-furanurononitriles have been prepared, their properties described as well as the methods used for the assignment of the configuration of the geometrical isomers. Some new reactions of the 6-bromo analog ( 1 ) of these compounds are reported. For example, when reacted with 2-mercaptoethanol or N,N′-dimethyl-ethylenediamine in the presence of NaOH, 1 gave the corresponding six-membered ring, stereo-isomers of an oxathiane or of a perhydrodiazine respectively. When the base used was Et₃N and the binucleophile the N-methyl-ethanolamine or the N,N′-dimethyl-ethylene-diamine the major product was a cyano-enamine which could be hydrolysed to a β-cyanoketone or cyclized to a five-membered ring, an oxazolidine or an imidazolidine respectively.     

Intramolecular metal-catalyzed amination of pseudo-anomeric C-H bonds

Intramolecular metal-catalyzed amination of a pseudo-anomeric C-H bond in a C-glycoside is reported. Treatment of α,β-C-carbamoyloxymethyl- or β-C-sulfamoyloxymethyl glycosides with Rh₂(OAc)₄, PhI(OAc)₂, and MgO provided original spirooxazolidines or spirooxathiazolidines in reasonable yields. No correlation between ‘anomeric’ stereochemistry and insertion efficiency was found for the conversion of carbamate derivatives whereas amination reactions of the corresponding sulfamate esters were found to be strongly dependent on the anomeric configuration.     

Application of the Novel Tandem Process Diels‐Alder Reaction/Ireland‐Claisen Rearrangement to the Synthesis of rac‐Juvabione and rac‐Epijuvabione

The novel tandem process Diels‐Alder reaction/Ireland‐Claisen rearrangement shows a high diastereoselectivity for the Ireland‐Claisen rearrangement starting from the endo‐product of the Diels‐Alder reaction. Based on this mechanistic knowledge, the novel tandem process could be applied to the synthesis of rac‐juvabione.     

Total Synthesis of Sanglifehrin A

The immunosuppressive agent sanglifehrin A has been prepared for the first time by total synthesis. The construction of the macrocyclic unit of the target molecule was achieved through a selective intramolecular Stille coupling, and the spirolactam unit by Paterson–aldol reactions. The final steps involve an intermolecular Stille coupling and the opening of the internal acetal unit. This convergent synthesis opens the way for the synthesis of libraries of novel sanglifehrin analogues for biological screening.     

Stereospecific Migration of P from N to C: Ring-Expansion Reaction of Chiral Diazaphospholidine Oxides

An addition-pseudorotation-elimination pathway is proposed for the first stereospecific ring-expansion reaction of chiral diazaphospholidine oxides by a 1,3-migration of P from N to C [Eq. (1)]. R=H, Ph; LDA=lithium diisopropylamide.