89578-36-9Relevant academic research and scientific papers
Asymmetric radical cyclization leading to β-lactams: Stereoselective synthesis of chiral key intermediates for carbapenem antibiotics PS-5 and thienamycin
Ishibashi, Hiroyuki,Kameoka, Chisato,Kodama, Kazuya,Ikeda, Masazumi
, p. 489 - 502 (2007/10/03)
A stereoselective synthesis of β-lactams by 4-exo-trig radical cyclizations of N-[2,2-bis(phenylthio)ethenyl]-α-bromo amides bearing a chiral inductor on the nitrogen atom has been examined. Bromide 8, upon treatment with Bu3SnH in the presence of AIBN in boiling benzene, gave a mixture of (4S)-2-azetidinone 12a and its (4R)-isomer 12b in a ratio of 71:29 and 69% combined yield. Similar treatment of α-bromobutanamide 11 with Bu3SnH afforded trans-(4S)-2-azetidinone 17a as the major product along with its (4R)-isomer 17b (70:30, 77% combined yield). Compound 17a was converted into 24, a chiral key intermediate in the synthesis of (+)-PS-5 (25). The cyclization of bromide 28 bearing an additional stereogenic center [(S)-oxygen functionality] at the side chain proceeded with much higher (4S)-stereoselectivity to give azetidinone 29a as the major product together with its (4R)-isomer 29b in a ratio of 78:22 and 40% combined yield. Compound 29a was converted, via an inversion of the oxygen functionality, into 37, a chiral key intermediate in the synthesis of (+)-thienamycin (38). A possible explanation for the observed diastereoselectivity in radical cyclization is presented.
Synthesis and Stereochemistry of Chiral Azetidin-2-ones and Azetidine-2-thiones. I. Synthesis of Diastereomeric 2- and 3-Substituted N-(α-Methylbenzyl)-β-aminopropionic Acids
Romanova, N. N.,Tallo, T. G.,Bundel', Yu. G.
, p. 375 - 377 (2007/10/03)
Nucleophilic addition of α-methylbenzylamine to the double bond of 2- and 3-substituted acrylic acids in pyridine under reflux proceeds nonstereoselectively.
Conformational and chiroptical properties of N-nitrosoazetidines
Shustov,Rauk
, p. 928 - 934 (2007/10/02)
Optically active N-nitrosoazetidines, containing the isolated nitrosoazetidine chromophore, i.e. (2R)-1-nitroso-2-methylazetidine (2) and (4S)-1-nitroso-2,2-dibutyl-4-methylazetidine (5), are synthesized, and their 1H NMR, CD, and UV spectra ar
STEREOCHEMISTRY OF THE METHYLATION OF THE (11S,4S) AND (11S,4R) DIASTEREOMERS OF 4-METHYL-1-(α-METHYLBENZYL)AZETIDIN-2-ONE
Romanova, N. N.,Tallo, T. G.,Borisenko, A. A.,Bundel', Yu. G.
, p. 761 - 766 (2007/10/02)
The methylation of the lithium derivatives of the (11S,4S) and (11S,4R) diastereomers of 4-methyl-1-(α-methylbenzyl)azetidin-2-one proceeds stereospecifically with the formation of only trans-(3S,4S)- and trans-(3R,4R)-dimethyl-1-(S
Diastereoface-Differentiating Synthesis of Substituted β-Lactams from Chiral Imines and/or Chiral α-Chloro Iminium Chlorides
Rogalska, Ewa,Belzecki, Czeslaw
, p. 1397 - 1402 (2007/10/02)
Reaction of imines carrying a chiral substituent at a nitrogen atom with symmetric or prochiral α-chloro iminium chlorides leads in a diastereoface-differentiating reaction to a mixture of diatereoisomeric or epimeric β-lactams.Attempts were made to determine the absolute configuration of obtained chiral β-lactams.Reaction of prochiral imines with chiral α-chloro iminium chlorides also provides mixtures of diastereomeric β-lactams or their enantiomers with a clear selectivity.
