The three-component reaction between a protected α-amino aldehyde, an alcohol and an α-silyloxymalononitrile provides an expedient access to protected α-hydroxy-β-amino acid derivatives. The prototypical process, performed on N-Cbz-phenylalaninal, is known...
SummaryThis paper reports an efficient preparation of bridged bis-β-CD AZO-CDim 1 bearing azobenzene as a linker and exhibiting high solubility in water. The photoisomerization properties were studied by UV–vis and HPLC and supported by ab initio calculations. The cis/trans ratio of AZO-CDim 1 is 7:93 without irradiation and 37:63 after 120 min of irradiation at 365 nm; the reaction is reversible after irradiation at 254 nm. The photoinduced, switchable binding behavior of AZO-CDim 1 was evaluated by ITC, NMR and molecular modeling in the presence of a ditopic adamantyl guest. The results indicate that AZO-CDim 1 can form two different inclusion complexes with an adamantyl dimer depending on its photoinduced isomers. Both cavities of cis-AZO-CDim 1 are complexed simultaneously by two adamantyl units of the guest forming a 1:1 complex while trans-AZO-CDim 1 seems to lead to the formation of supramolecular polymers with an n:n stoichiometry.
Using Garner’s aldehyde as
a substrate, one-pot MAC hydroxyhomologation
reactions proceeded in good yields and with anti selectivity
for the first time (dr up to 9:1). The products were used to prepare
a panel of protected derivatives of erythro-β-hydroxyaspartic
acid and erythro-β-hydroxyasparagine as single
enantiomers in a few steps.
The synthesis of a new class of thiosugar derivatives, 1,5-dithio-1-enopyranosides, has been achieved in a two-step sequence from easily available aldofuranoses. In the first step, a carbohydrate-derived ketene dithioacetal was formed by Peterson olefination of an aldofuranose and a lithiated α-silyl thioacetal. In the second step, intramolecular nucleophilic
In this study we describe the first synthesis of an alkyne-based trehalose monomycolate probe closely mimicking the complex pattern of mycolic acids and its utility for the study of mycomembrane and mycoloyltransferases in Corynebacteria.
The asymmetric total synthesis of the originally proposed structure of gymnangiamide, a cytotoxic pentapeptide isolated from the marine hydroid Gymnangium regae Jaderholm, has been achieved. Key to the synthesis was the use of asymmetric hydrogenation of alpha-substituted beta-ketoesters through dynamic kinetic resolution for the preparation of nonproteinogenic chiral amino acids. The disparity of the NMR spectra between the synthetic material containing the L-serine residue and the natural product required a revision of the proposed structure.
The stereoselective synthesis of the cis‐γ,δ‐disubstituted α,β‐unsaturated δ‐lactone fragment of the leustroducsins or phoslactomycins was accomplished. The new synthetic strategy involves a catalytic asymmetric ketene–aldehyde [2+2] cycloaddition leading to the formation of a cis‐disubstituted β‐lactone. Ring extension by enolate condensation and subsequent recyclisation then gave the target δ‐lactone in a straightforward fashion. Coupling studies with cyclohexanone are also reported.
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