Steric Factors affecting the Specificity of Polyglycosidases

Nature ◽  
1960 ◽  
Vol 187 (4743) ◽  
pp. 1110-1111 ◽  
Author(s):  
F. W. PARRISH ◽  
A. S. PERLIN
Keyword(s):  
Factors Affecting ◽  
Steric Factors

Nickel(II) and palladium(II) complexes with acylhydrazone ligands of α-diketones: the electronic and steric factors affecting the formation of the dimeric palladium(II) complexes

1999 ◽  
Vol 295 (2) ◽  
pp. 171-179 ◽  
Author(s):  
Alessia Bacchi ◽  
Mauro Carcelli ◽  
Paolo Pelagatti ◽  
Corrado Pelizzi ◽  
Giancarlo Pelizzi ◽  
...  
Keyword(s):  
Factors Affecting ◽  
Steric Factors

Factors affecting product formation in the photolysis of α-spirocyclopropyl ketones

1983 ◽  
Vol 61 (5) ◽  
pp. 936-945 ◽  
Author(s):  
Peter Yates ◽  
Patrick Hugh Helferty
Keyword(s):  
Solvent Effect ◽  
Product Formation ◽  
Major Product ◽  
Ring Size ◽  
Factors Affecting ◽  
Hydrocarbon Solvents ◽  
Steric Factors

Photolysis of spiro[2.5]oct-7-en-4-ones results in exclusive β-cleavage in methanol to give 2-ethenylcyclohex-2-en-1-ones and in hydrocarbon solvents to give (E)- and (Z)-2-ethylidenecyclohex-3-en-1-ones. The solvent effect is ascribed to the role of methanol in stabilizing trienol intermediates and engendering their intermolecular ketonization. Photolysis of 8-methylenespiro[2.5]octan-4-ones in methanol gives 2-ethenylcyclohex-2-en-1-ones and bicyclo[4.3.0]non-1(6)-en-2-ones; irradiation in methanol-O-d indicates that the former type of product is formed mainly via a trienol intermediate. Photolysis of 8-methylenespiro[2.5]octan-4-ones in benzene gives 2-ethenylcyclohex-2-en-1-ones together with (E)- and (Z)-2-ethylidene-3-methylenecyclohexan-1-ones; the latter undergo photoconversion to the former during the irradiation. 6,6-Dimethylspiro[2.4]-heptan-4-one on photolysis in methanol undergoes ct-cleavage to give 4-methoxy-7,7-dimethyl-5-oxaspiro[2.5]octane as the major product, whereas under the same conditions 6,6-dimethylspiro[2.5]octan-4-one is reduced to the corresponding alcohol and 6,6,8-trimethylspiro[2.5]octan-4-one undergoes β-cleavage to give 2-ethyl-3,5,5-trimethylcyclohexan-1-one as the major primary product; this trichotomy is interpreted in terms of ring-size and steric factors.

Reduction of cyclic anhydrides. II. Factors affecting regioselectivity of attack on the carbonyl group by metal hydrides

1978 ◽  
Vol 56 (11) ◽  
pp. 1524-1532 ◽  
Author(s):  
Margaret M. Kayser ◽  
Peter Morand
Keyword(s):  
Carbonyl Group ◽  
Metal Hydride ◽  
Metal Hydrides ◽  
Factors Affecting ◽  
Preferential Formation ◽  
Factors Influencing ◽  
Steric Factors ◽  
Cyclic Anhydrides ◽  
Experimental Findings ◽  
Carbonyl Function

The reduction of unsymmetrically substituted cyclic anhydrides with metal hydrides often leads to the preferential formation of one of the two possible lactones. In the light of recent experimental findings and theories concerning metal hydride addition to the carbonyl function, the electronic and steric factors influencing regioselectivity of cyclic anhydride reductions are discussed and an explanation for the observed patterns is proffered. Similar considerations may be extended to predict the major lactonic products in the reductions of various other unsymmetrical cyclic anhydrides.

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