Silylcupration of (R)-2,2-Dimethyl-3-(tert-butoxycarbonyl)-4-ethynyloxazolidine:  A Stereoselective Approach to the Synthesis of γ-Silylated Saturated and Unsaturated α-Amino Acids

Abstract

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New enantiomerically enriched amino allyl- and allenylsilanes derived from naturally occurring amino acids

“…Trimethylsilylcyanocuprate was prepared according to the general route, 28 using hexamethyldisilane (642 mg, 4.4 mmol), MeLi (1,5 mL, 1.6 M solution in THF, 2.2 mmol) and CuCN (94 mg, 1.1 mmol) and was cooled to À78°C. Amino acetate 2b (270 mg, 1 mol) was dissolved in THF, added at À78°C and left at this temperature for 30 min.…”

“…The purification was performed twice (first eluent: petroleum ether/ethyl acetate = 20/1, second eluent: petroleum ether/ethyl acetate = 10/1) to give 265 mg of (S,R)-anti-5 as a colourless oil (yield: 42%) and 182 mg of (S,S)-syn-5 (yield 29%). Trimethylsilylcuprate (1.1 equiv) was prepared according to the general route, 28 and the solution was cooled to À78°C. Acetate (S,R)-anti-5 (150 mg, 0.5 mmol) was dissolved in THF (2.5 mL) and added dropwise.…”

“…Compound (R,S)-6 must be stored at À20°C, as rapidly decomposes at room temperature. Trimethylsililcuprate (1.5 equiv) was prepared according to the general route, 28 and the solution cooled to À78°C. Acetate (S,R)-anti-5 (80 mg, 0.3 mmol) was dissolved in THF (1.5 mL) and added dropwise.…”

Chemistry of Silicon‐Containing Amino Acids

“…[31].Scheme 6.7 Two preparations of b-phenyldimethylsilylalanine.Scheme 6.6 Asymmetric synthesis of b-dimethylphenylsilylalanine.…”

Chirality transferring [3,3] sigmatropic rearrangement of (1‐acyloxy‐2‐alkenyl)trialkylsilane synthesis of optically active vinylsilane‐containing α‐amino acid

“…3,4 We envisioned that the use of ␣-amino acid as the acyloxy group 5 would produce vinylsilane-containing ␣-amino acid 2 in which the original chirality at the ␣-acyloxy carbon would be transferred into the newly formed consecutive chiral centers. Furthermore, the vinylsilane-containing amino acid can be viewed not only as a novel class of unusual amino acid 6 but also as a useful synthetic precursor for a variety of biologically active amino acids. In this report, we describe highly diastereoselective [3,3] sigmatropic rearrangement of ␣-amino-acyloxy trialkylsilane 1, which afforded a siliconcontaining ␣-amino acid and ␣,␣-disubstituted ␣-amino acid 2 in optically active form.…”