Addition of Purines to N-Boc Imines Generated in Situ in Water: Efficient Synthesis of Novel Acyclic Purine Azanucleosides
摘要:
A mild, efficient and highly regioselective addition of purine derivatives to N-Boc imines generated in situ in water was developed for the first time. A wide range of novel acyclic purine azanucleosides were synthesized in moderate to high yields through this transformation. This methodology was also appropriate for some other N-heterocycles.
Phase Transfer Catalyzed Enantioselective Strecker Reactions of α-Amido Sulfones with Cyanohydrins
作者:Raquel P. Herrera、Valentina Sgarzani、Luca Bernardi、Francesco Fini、Daniel Pettersen、Alfredo Ricci
DOI:10.1021/jo061566u
日期:2006.12.1
A study into the use of a chiral phase-transfer catalyst in conjunction with acetone cyanohydrin to effect the enantioselective formation of α-amino nitriles from α-amido sulfones is described. This novel catalytic asymmetric Streckerreaction is analyzed with regard to the possible mechanistic basis.
The unprecedented use of phase-transfer catalysis (PTC) in an asymmetric hydrophosphonylation reaction allows the obtainment of a range of optically active α-amino phosphonic acid derivatives directly from α-amido sulfones.
ammonium chlorides to provide the corresponding aza-Henry adducts in good yields and very high selectivities. It represents the first general enantioselectiveaza-Henry method for azomethines derived from enolizable aldehydes, giving rise to enantiomeric excesses above 94%. In addition, the reactions with nitroethane afforded high diastereo- and enantioselectivities (syn:anti up to 95:5; up to 98% ee for syn)
Optically active beta-amino-alpha-methylene carbonyl derivatives (aza-Morita-Baylis-Hillman adducts) were prepared using a one-pot protocol involving an enantioselective Mannich reaction catalyzed by various quinine-based catalysts, followed by a Horner olefination.
Asymmetric Aza-Henry Reaction Under Phase Transfer Catalysis: An Experimental and Theoretical Study
value of the methodology described is demonstrated by providing (a) a direct route for the asymmetricsynthesis of differently substituted 1,2-diamines and (b) a new asymmetricsynthesis of gamma-amino alpha,beta-unsaturated esters through a catalytic, highly enantioselective formal addition of functionalized alkenyl groups to azomethines. Finally, a preferred TS that nicely fits the observed enantioselectivity