31551-66-3Relevant academic research and scientific papers
Asymmetric synthesis of β-substituted γ-lactams employing the samp-/ramp-hydrazone methodology. Application to the synthesis of (R-(-)-baclofen
Enders, Dieter,Niemier, Oliver
, p. 385 - 403 (2007/10/03)
A short and efficient asymmetric synthesis of β-substituted γ-lactams is described. Key steps are the α-alkylation of aldehyde SAMP-hydrazones with alkyl bromoacetates, their MMPP mediated conversion to the corresponding nitriles and a reductive cyclization with Raney Ni or Ni boride to the title pyrrolidin-2-ones. The β-substituted γ-lactams are obtained in three steps, good overall yields (27-78%) and excellent enantiomeric excesses (ee=93-99%). The applicability of this procedure for the asymmetric synthesis of GABAs (γ-aminobutyric acids) is demonstrated for (R-(-)-baclofen hydrochloride, which is obtained in 4 steps 55% yield and 94% ee.
Oxyoxazolidinone as an auxiliary for heterocyclic synthesis. Enantioselective formation of N-unprotected 2-pyrrolidones from selenocarboxylate and allylamines via radical cyclization
Kamimura, Akio,Omata, Yoji,Tanaka, Keiichi,Shirai, Masashi
, p. 6291 - 6299 (2007/10/03)
Optically active N-unprotected 2-pyrrolidones were prepared in a highly stereoselective manner through radical cyclization reaction of oxyoxazolidinone. Asymmetric induction from the oxyoxazolidinone ring system was generally high and oxazabicyclo[3.3.0]octanones were obtained in good yields. Treatment of the bicyclic compounds with TBAF resulted in the one-step cleavage of C-O and C-N bond, directly giving secondary 2-pyrrolidones in good yields along with recovery of chiral mandelic acid without loss of optical purity. The use of the present procedure gave optically active 4,5-disubstituted N-unprotected 2-pyrrolidone derivatives trans selectively.
Stereoselective formation of optically active 2-oxy-1,3-oxazolidin-4-ones and an efficient synthesis of optically active secondary 2-pyrrolidones
Omata, Yoji,Kakehi, Akikazu,Shirai, Masashi,Kamimura, Akio
, p. 6911 - 6914 (2007/10/03)
Treatment of (-)-O-acyllactamides or mandelamides with TBSOTf in the presence of base gives optically active 2-oxy-1,3-oxazolidin-4-ones stereoselectively, which serve as useful precursors for the preparation of optically active secondary 2-pyrrolidones via radical cyclization and subsequent one-step removal of mandelic acid.
Cycloaddition Reactions of Chiral 2-Amino-1,3-butadienes with Nitroalkenes: Synthesis of Enantiomerically Pure 4-Nitrocyclohexanones
Barluenga, Jose?,Aznar, Fernando,Ribas, Cristina,Valde?s, Carlos
, p. 6746 - 6753 (2007/10/03)
2-Amino-1,3-butadienes bearing commercially available S-(+)-2-(methoxymethyl)pyrrolidine as chiral auxiliary undergo a [4 + 2] cycloaddition reaction with nitroalkenes to furnish 4-nitrocyclohexanones upon hydrolysis of the resulting enamine. The cycloadd
The Synthesis of Aracemic 4-Substituted Pyrrolidinones and 3-Substituted Pyrrolidines. An Asymmetric Synthesis of (-)-Rolipram
Meyers, A. I.,Snyder, Lawrence
, p. 36 - 42 (2007/10/02)
Conjugate additions of RCuCNLi to the chiral α,β-unsaturated lactam 4 gives almost exclusive exo addition - a reversal in stereochemistry when cuprates were added to chiral lactam 1.The lactams 5 were transformed into 4-substituted pyrrolidinones 8 via a three-step sequence which involved decarbalkoxylation, silane reduction and metal-ammonia benzylamine cleavage.The chemical yields as well as the enantiomeric purity were very high for this process.As an example of the usefulness of this scheme, the antidepressant (-)-Rolipram was prepared in good overall yield.Furthermore, the bicyclic lactams 6 were readily transformed, using alane as the reducing agent, to 3-substituted pyrrolidines 11.Absolute configurations of 8 and 11 were confirmed by comparison with literature assignments which also gave strong support to the facial addition of the cuprates to 4.
