Exploring the Metal‐Catalyzed Reactions of α‐Diazo‐β‐hydroxyamino Esters: Conversion of Cyclic Aldonitrones into Ketonitrones

Abstract

International audienc

Ring‐Junction‐Substituted Polyhydroxylated Pyrrolizidines and Indolizidines from Ketonitrone Cycloadditions

“…With ketonitrone 9 in hand, we decided to investigate its reactivity in 1,3‐dipolar cycloaddition reactions, and compare it to the reactivity of the corresponding aldonitrone 1 . Due to the increased steric bulk of ketonitrone 9 , we anticipated that it might be less reactive than 1 , and so we started to study its cycloaddition reactions with highly reactive alkynes (Scheme ).…”

“…The stereoselectivity of the cycloaddition was slightly better with homoallyl alcohol; isoxazolidines 20a and 20b were formed in an 85:15 ratio (Table , entries 4 and 5). The yield and diastereoselectivity of the cycloaddition turned out to be substrate dependant; the cycloaddition of nitrone 21 with allylic alcohol gave isoxazolidines 22a and 22b in 70 % yield, in a 90:10 ratio (Table , entries 6 and 7).…”

“…Recently, we disclosed an efficient two‐step method for the transformation of cyclic aldonitrones into ketonitrones, and we decided to explore the reactivity of these ketonitrones in 1,3‐dipolar cycloaddition reactions for the synthesis of polyhydroxylated pyrrolizidines and indolizidines bearing a quaternary centre at the ring junction. Our results, including the evaluation of the newly synthesised polyhydroxylated heterocycles as glycosidase inhibitors, are reported in this paper.…”

Aziridination of Cyclic Nitrones Targeting Constrained Iminosugars

“…Surprisingly, while cycloaddition of cyclic carbohydrate-derived nitrones with alkenes has been widely applied, 18 their cycloaddition with alkynes has never been described. 19 Our study thus began by investigating the regio-and stereoselectivity of alkyne cycloaddition with nitrones 2a−e (Scheme 3, Table 1). Nitrone 2a and phenylacetylene (used as solvent) were first allowed to react at room temperature until complete conversion of the starting nitrone (2 days).…”

“…Therefore, each step of this transformation was studied separately. Surprisingly, while cycloaddition of cyclic carbohydrate-derived nitrones with alkenes has been widely applied, their cycloaddition with alkynes has never been described . Our study thus began by investigating the regio- and stereoselectivity of alkyne cycloaddition with nitrones 2a – e (Scheme , Table ).…”