Umsetzung von <i>N</i>‐Carbonyl‐sulfamidsäurechlorid mit Olefinen. α.β‐Disubstituierte β‐Lactame

Bestian, H.; Biener, Hans; Clauß, Karl; Heyn, Hartmut

doi:10.1002/jlac.19687180109

Cited by 39 publications

(19 citation statements)

References 7 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…[16] Initial screening of commercial lipases, esterases and proteases for their ability to catalyze hydrolysis of ( AE )-1 revealed several that catalyzed the hydrolysis, but with low enantioselectivity. [17] The most promising hydrolase was lipase B from Candida antarctica (Novozym 435, CAL-B) since it was slightly enantioselective (E 5, Table 1, row 1).…”

Section: Cal-b-catalyzed Ring Opening Of B-lactamsmentioning

confidence: 99%

Molecular Basis for the Enantioselective Ring Opening of β‐Lactams Catalyzed by Candida antarctica Lipase B

et al. 2003

View full text Add to dashboard Cite

Lipase B from Candida antarctica (CAL-B) catalyzes the slow, but highly enantioselective (E >200), ring-opening alcoholysis of two bicyclic and two 4-aryl-substituted b-lactams. Surprisingly, the rate of the reaction varies with the nature of the alcohols and was fastest with either enantiomer of 2-octanol. A 0.5-g scale reaction with 2-octanol as the nucleophile in diisopropyl ether at 60 8C yielded the unreacted b-lactam in 39 ± 46% yield (maximum yield is 50%) with ! 96% ee. The product b-amino acid esters reacted further by polymerization (not isolated or characterized) or by hydrolysis due to small amounts of water in the reaction mixture yielding bamino acids (7 ± 11% yield, ! 96% ee). The favored enantiomer of all four b-lactams had similar 3-D orientation of substituents, as did most previously reported b-lactams and b-lactones in similar ringopening reactions. Computer modeling of the ring opening of 4-phenylazetidin-2-one suggests that the reaction proceeds via an unusual substrate-assisted transition state, where the substrate alcohol bridges between the catalytic histidine and the nitrogen of the b-lactam. Computer modeling also suggested that the molecular basis for the high enantioselectivity is a severe steric clash between Ile189 in CAL-B and the phenyl substituent on the slow-reacting enantiomer of the b-lactam.

show abstract

Section: Cal-b-catalyzed Ring Opening Of B-lactamsmentioning

confidence: 99%

Molecular Basis for the Enantioselective Ring Opening of β‐Lactams Catalyzed by Candida antarctica Lipase B

et al. 2003

View full text Add to dashboard Cite

show abstract

“…Ziegler originally reported that the thermal dimerization of 19 gave a single cyclodimer.44 More recent work by Leitich showed that three cyclodimers were formed. 40 The structures were assigned as the trans,trans (syn) (20), the trans,cis (21), and the trans,trans (anti) (22) dimers in the ratio of 10:4:1.…”

Section: Discussionmentioning

confidence: 99%

[2+2] thermal cyclodimerization of cis, trans-1,3-cyclooctadiene

Padwa¹,

Koehn²,

Masaracchia³

et al. 1971

J. Am. Chem. Soc.

View full text Add to dashboard Cite

When heated, neat or in hydrocarbon solvent, cis,trans-\,3-cyclooctadiene underwent both dimerization and isomerization. The structures of the 2 + 2 cyclodimers were assigned as the trans.cis, trans.trans, and cis,cis dimers. The ratio of the three dimers was found to be independent of the reaction temperature. The reaction followed good second-order kinetics and has /í* = 19 kcal/mol and 5+ = -10 eu. The results have been rationalized on the basis of a stepwise mechanism for dimer formation.he concerted, suprafacial, thermal fusion of two olefins to form a cyclobutane ring is a symmetryforbidden process.4 In accord with this prediction, thermal "1,2" cycloadditions of simple olefins have been shown to involve diradical intermediates.5 Thermal cycloaddition can, in theory, proceed in a concerted symmetry-allowed fashion by a (tt2s + ir2a) combination of the two 7 bonds.4 The high degree of stereospecificity in the 2 + 2 cycloaddition of olefins with alienes,6-12 ketenes,13-19 and reactive isocyanates20'21 points toward the possibility that these reactions are concerted. It appears that a cumulative -bond system can function more readily as a Tr2a donor than an isolated double bond. Orbital symmetry theory applied to the concerted fragmentation of cyclobutane demands that the process occur via the (

show abstract

“…A weak band at 1740 cm-' can be assigned to a carbonyl absorption also present in spectra of 0-y-unsaturated carbonamide-N-sulfonylchlorides (7). Bands appearing at 1175 and 1405 cm-' are an indication for the occurrence of -S02C1 groups.…”

mentioning

confidence: 83%

Reaction of N‐chlorosulfonylisocyanate with unsaturated polymers. Route to a synthesis of polyampholytes

Does

Hofman

Utteren

1973

J. Polym. Sci. B Polym. Lett. Ed.

View full text Add to dashboard Cite

Umsetzung von N‐Carbonyl‐sulfamidsäurechlorid mit Olefinen. α.β‐Disubstituierte β‐Lactame

Cited by 39 publications

References 7 publications

Molecular Basis for the Enantioselective Ring Opening of β‐Lactams Catalyzed by Candida antarctica Lipase B

Molecular Basis for the Enantioselective Ring Opening of β‐Lactams Catalyzed by Candida antarctica Lipase B

[2+2] thermal cyclodimerization of cis, trans-1,3-cyclooctadiene

Reaction of N‐chlorosulfonylisocyanate with unsaturated polymers. Route to a synthesis of polyampholytes

Contact Info

Product

Resources

About