The synthesis of (αS,2R)-(2,5-dihydro-1H-pyrrol-2-yl)glycine (22, normethylazafuranomycin) by the gold-catalyzed cycloisomerization of α-aminoallene 17 is described. The target molecule was synthesized in 13 linear steps from Cbz-protected Garner aldehyde (R)-2 in an overall yield of 2.4%. The approach was first examined in model studies, which afforded the alkylated azafuranomycin derivative 1...

Stereoselective synthesis of the 16-membered diolide 27, a fully functionalized congener of lepranthin (1), is described. The requisite five asymmetric carbon centers in monomer 23 were constructed in a highly stereoselective manner by using different epoxide-opening reactions of α,β-unsaturated γ,δ-epoxy esters and epoxy alcohol derivatives as the key steps. The monomer 23 was successfully tra...

First regioselective ring opening of serine derived cyclic sulfamidate by hard nucleophiles like ArONa is developed, where β-elimination of serine sulfamidate ester by stronger nucleophiles is overcome by reversal of the electronic effect of the carboxylate anion. This method provides easy and direct access to a variety of N-Boc- and N-PMB protected β-aryloxy-α-amino acids with complete retenti...

An efficient route for the synthesis of all four diastereomers of PMP-protected α-amino-γ-butyrolacton to access γ-hydroxynorvaline was established. The asymmetric key steps comprise an organocatalytic Mannich reaction and an enzymatic ketone reduction. Three reaction steps could be integrated in a one-pot process, using 2-PrOH both as solvent and as reducing agent. The sequential construction ...

A new class of peptidomimetic is reported in which one of the amide C=O bonds of the peptide backbone is replaced by an oxetane ring. They are synthesised by conjugate addition of various α-amino esters to a 3-(nitromethylene)oxetane, reduction of the nitro group and further coupling with N-Z protected amino acids to grow the peptide chain. Structural insights are provided by X-ray diffraction ...

An enantioselective β-carbon amination for enals is disclosed. The nitrogen atom from a protected hydrazine with suitable electronic properties readily behaves as a nucleophile. Addition of the nitrogen nucleophile to a catalytically generated N-heterocyclic-carbene-bound α,β-unsaturated acyl azolium intermediate constructs a new carbon-nitrogen bond asymmetrically. The pyrazolidinone products ...

Differentially protected 1,2-diols were synthesized by enantioselective aldehyde α-oxygenation followed by organomagnesium or -lithium addition. Contrary to a previous report, the resultant diols possess an anti configuration. Good selectivity was achieved regardless of the hybridization state of the nucleophile or the presence or absence of branching. This method was applied to short syntheses...

The propensity of a half-sandwich (η5-tetramethylcyclopentadienyl) dimethylsilylamido Ti-based catalyst bearing an auxiliary diethylboryl-protected pyridyl moiety (Ti-8), activated by methylaluminoxane (MAO) to homopolymerize α-olefins such as ethylene, 1-hexene and styrene as well as to copolymerize styrene with 1,3-cyclohexadiene is described. The reactivity of Ti-8 was investigated in compar...

Aminooxyl sugar derivatives are versatile building blocks for the generation of various glycoconjugates with interesting bioactivities. We report herein a synthetic method for the preparation of orthogonally protected glycoaminooxy acid from methyl α-d-glycopyranoside in 7 steps. The key steps involve the selective protection, O-alkylation and Mitsunobu reaction. Fully deprotected N-oxyamide-li...

Introduction During an evaluation of azido-α-amino acids and their utility in solid-phase peptide chemistry, the octapeptide angiotensin II and a tripeptide thyrotropin-releasing hormone (TRH) analog have been prepared using Meldal’s procedure [1]. A necessary novel step was the reduction of the azido moiety of L-proline, a secondary amine constrained by a ring, to the corresponding free amine ...