Stereoselective, nonracemic synthesis of ω-borono-α-amino acids

The Suzuki cross-coupling reaction: a powerful tool for the attachment of organometallic ‘NCN’-pincer units to biological scaffolds

“…For this purpose, we have chosen the SuzukiÁ/Miyaura cross-coupling reaction of the protected allyl glycine ester 2 [13] and the bifunctional precursor I Ã/NCNÃ/Br 1 (Scheme 1). The borane intermediate formed by reaction of 2 with 9-BBN (9-borabicyclo[3.3.1]nonane) was reacted with 1 using [PdCl 2 (dppf)] as catalyst.…”

“…DMF was flash-distilled from CaH 2 and stored on molecular sieves. The Pt salt [Pt(m-SEt 2 )(p -tol) 2 ] 2 [19], the ligand precursor [I Ã/NCN Ã/Br] 1 [7], and compounds 2 [13] [16] were prepare according to published procedures. All other reagents were obtained commercially and used without further purification.…”

Novel 3‐Carboxy‐ and 3‐Phosphonopyrazoline Amino Acids as Potent and Selective NMDA Receptor Antagonists: Design, Synthesis, and Pharmacological Characterization

“…Volatiles were removed under reduced pressure, and the residue was crystallized from EtOH/Et 2 Synthesis of (5S,aR)-1, (5R,aS)-1, (5R,aR)-2, and (5S,aS)-2. The synthetic procedure described for racemates (AE )-1 and (AE )-2 was also used to obtain the pure enantiomers (5S,aR)-1, (5R,aR)-2, (5R,aS)-1 and (5S,aS)-2, starting from alkenes (R)-6 [15] and (S)-6, [16] respectively. methyl]-phosphonate 13 [17] (2.61 g, 8.50 mmol) and solid NaHCO 3 (2.40 g, 28.57 mmol) were added to a solution of (R)-6 (1.30 g, 5.70 mmol) in EtOAc (25 mL).…”

“…The synthetic approach described for the racemates was also applied to the synthesis of enantiomerically pure amino acids (5S,aR)-1, (5R,aR)-2, (5R,aS)-1, and (5S,aS)-2, starting from enantiopure dipolarophile (R)-6 [15] or (S)-6, [16] respectively (Scheme 1). Intermediate (À)-8 was crystallized successfully from diisopropyl ether/hexane and, thus, was able to be submitted for X-ray analysis.…”

Ring-Closing Alkyne Metathesis Approach toward the Synthesis of Alkyne Mimics of Thioether A-, B-, C-, and DE-Ring Systems of the Lantibiotic Nisin Z

“…Alkylation of the Gly/Ni/BPB-complex with 1-Bromo-2-butyne: The Gly/Ni/BPB-complex 4,5 (6 g, 12 mmol) and NaOH (1.2 g, 30 mmol) were dissolved in CH 3 CN (60 mL) and 1-bromo-2-butyne (1.2 mL, 13.4 mmol) was added dropwise. The deeply red mixture was stirred for 1.5 h at room temperature.…”