syn/anti Switching by Specific Heteroatom–Titanium Coordination in the Mannich‐Like Synthesis of 2,3‐Diaryl‐β‐amino Acid Derivatives

Abstract

A very efficient synthesis of 2,3‐diaryl‐β‐amino acid derivatives is realized by a TiCl4/triethylamine‐catalyzed Mannich‐like reaction of arylacetic or arylthioacetic esters with arylimines. The presence on the arylacetic moiety of an ortho‐heteroatom group able to coordinate to the titanium center is of dramatic importance for the outcome of the reaction and to tune the syn/anti diastereoselection. In particular, with o‐F‐, o‐Cl‐, and o‐Br‐arylacetates, the syn adduct was isolated as the largely prevalent isomer. When (–)‐8‐phenylmenthyl (2‐fluorophenyl)acetate was used, the condensation with imines resulted in high diastereo‐ and enantioselectivity. In agreement with the stereochemical results and NMR studies, a conceivable reaction mechanism was proposed.

Electrospinning of pyrazole-isothiazole derivatives: nanofibers from small molecules

“…The insertion of unnatural amino acids in the peptide sequences is a very established tool to overcome this problem. Starting from this consideration, and continuing our research on the preparation of non-coded amino acids and on their use to obtain peptidomimetics [24][25][26][27] for different applications ranging from biomedical application to nanomaterials, we investigated the electrospinnability of short peptide chains. In this work we used simple systems formed by natural amino acids coupled with an unnatural amino acid, i.e.…”

Unusual Chemoselective RhII‐Catalysed Transformations of α‐Diazocarbonyl Piperidine Cores

“…The protection of the nitrogen atom of 3 with a Boc group was performed by treatment with (tBuOCO) 2 O in the presence of triethylamine (TEA) in CH 2 Cl 2 at 0 8C then at 25 8C (1 h) to afford 4 a (92 %). Similarly, derivative 4 b (98 %) was obtained from 3 and iBuOCOCl (TEA/CH 2 Cl 2 , 08C, 4 h; Scheme 1) Tetrahydroisoquinoline-4-carboxylic acid 8, substituted at C3 with an aryl moiety, was prepared from b-amino ester 5 [12] by a Pictet-Spengler reaction (Scheme 2). The reaction directly from 5 failed under several reaction conditions.…”

“…b-Amino ester 5 was prepared according to a reported procedure. [12] Ethyl 4-tert-butoxycarbonyl-1,2,3,4-tetrahydroisoquinoline-…”

Self-assembled hydrophobic Ala-Aib peptide encapsulating curcumin: a convenient system for water insoluble drugs

“…9 They are easily synthesized using solid-phase methods where the peptide sequence could be specically modied at molecular levels. 10 In particular, the use of non-coded amino acids [11][12][13][14][15] in the peptide sequence is of particular relevance due to their ability to stabilize secondary structures such as a-helices, turn and b-sheets. [16][17][18][19] Furthermore, they were used for driving the self-assembly processes, modulating the shape and dimension of the aggregates, [20][21][22] expanding the scope of the nanoarchitectures that can be obtained.…”