Syntheses related to the carbohydrate moiety in lincomycin

1969 ◽  
Vol 47 (1) ◽  
pp. 75-79 ◽  
Author(s):  
G. B. Howarth ◽  
D. G. Lance ◽  
W. A. Szarek ◽  
J. K. N. Jones
Keyword(s):  
Crystalline Form ◽  
Carbohydrate Moiety ◽  
Allylic Alcohols ◽  
Nitro Derivatives ◽  
Sugar Derivatives ◽  
Cis And Trans

Addition of nitroethane to 1,2:3,4-di-O-isopropylidene-α-D-galacto-hexodialdo-1,5-pyranose (3) gave a mixture of β-nitro alcohols (4), which was acetylated to afford a mixture of β-nitro acetates (5). Dehydroacetylation of the latter gave cis- and trans-6,7,8-trideoxy-1,2:3,4-di-O-isopropylidene-7-C-nitro-α-D-galacto-oct-6-enose (6 and 7) in a ratio of about 6:1, respectively. Addition of ammonia to the cis-nitroolefin (6) gave rapidly a mixture of two stereoisomeric vic-nitroamines (8), which was acetylated to furnish a mixture of two 6-acetamido-6,7-dideoxy-7-C-nitro derivatives (9). The same products (9) were obtained by the action of ammonia in aqueous tetrahydrofuran upon the preponderant β-nitro acetate, followed by acetylation. Vinylation of the aldehyde 3 gave a mixture of allylic alcohols (10); the preponderant epimer was obtained pure in crystalline form. The various 8-carbon sugar derivatives are of interest as potential intermediates in the synthesis of the carbohydrate moiety in lincomycin.

Nitration of 3,4-Dimethylacetophenone and 3,4-Dimethylbenzophenone. Formation and Rearomatization of Adducts

1975 ◽  
Vol 53 (11) ◽  
pp. 1570-1578 ◽  
Author(s):  
Alfred Fischer ◽  
Colin Campbell Greig ◽  
Rolf Röderer
Keyword(s):  
Acetic Acid ◽  
Acetic Anhydride ◽  
Nitro Group ◽  
Nitrous Acid ◽  
Main Product ◽  
Intermediate Formation ◽  
Nitro Derivatives ◽  
Acidic Conditions ◽  
Cis And Trans ◽  
Derivatives Of

Nitration of 3,4-dimethylacetophenone in acetic anhydride gives a mixture of cis-and trans-2-acetyl-4,5-dimethyl-4-nitro-1,4-dihydrophenyl acetate as the main product, together with 3,4-dimethyl-2-, 3,4-dimethyl-5-, and 3,4-dimethyl-6-nitroacetophenone. Analogous products are obtained from 3,4-dimethylbenzophenone. Rearomatization of the adducts under mildly acidic conditions occurs via 1,4-elimination of nitrous acid to form 2-acetyl- and 2-benzoyl-4,5-dimethylphenyl acetate, respectively. In strongly acidic conditions elimination of acetic acid accompanied by 1,2- and 1,3-shifts of the nitro group occurs to form the 2- and 5-nitro derivatives of the parent ketones. The rearomatization to the nitro derivatives involves the intermediate formation of an ipso-cyclohexadienyl cation which may be trapped by anisole or mesitylene to form biphenyl derivatives.

Nitration of 1-chloro-2,3-dimethylbenzene in acetic anhydride. Formation and rearomatization of adducts

1978 ◽  
Vol 56 (8) ◽  
pp. 1063-1068
Author(s):  
Alfred Fischer ◽  
Colin Campbell Greig
Keyword(s):  
Acetic Acid ◽  
Acetic Anhydride ◽  
Nitrous Acid ◽  
Major Product ◽  
Trans Isomers ◽  
Cis And Trans Isomers ◽  
Nitro Derivatives ◽  
Subsequent Elimination ◽  
And Migration ◽  
Cis And Trans

Nitration of l-chloro-2,3-dimethylbenzene in acetic anhydride gives the cis and trans isomers of 3-chloro-4,5-dimethyl-4-nitrocyclohexa-2,5-dienyl acetate (29%) and l-chloro-2,3-dimethyl-4-nitro- (46%), -5-nitro- (5%), and -6-nitrobenzene (20%). In formic acid and acidified methanol, exchange of acetate for formate and methoxyl, respectively, occurs and the diastereoisomers of 3-chloro-4,5-dimethyl-4-nitrocyclohexa-2,5-dienyl formate and methyl ether, respectively, are formed. Rearomatization of each isomer of 3-chloro-4,5-dimethyl-4-nitrocyclohexa-2,5-dienyl acetate in acetic acid results in initial isomerization to form the pair of diastereoisomers and subsequent elimination of nitrous acid to form 3-chloro-4,5-dimethylphenyl acetate. In 25% trifluoroacetic acid in deuteriochloroform elimination of acetic acid and migration of the nitro group to form 1-chloro-2,3-dimethyl-4-nitro-benzene and a lesser amount of its 6-nitro isomer is the dominant reaction. In the presence of mesitylene the formation of the nitro derivatives is suppressed and 3′-chloro-2,4,4′,5′,6-pentamethylbiphenyl is obtained. It is proposed that cyclohexadienyl cations are significant intermediates in ail of the reactions. Pyrolysis of the adducts gives 1-chloro-2,3-dimethylbenzene as the major product.

ChemInform Abstract: A Novel Thermal Rearrangement of Allylic Nitro Derivatives into Allylic Alcohols.

ChemInform ◽  
1990 ◽  
Vol 21 (1) ◽  
Author(s):  
J. BOIVIN ◽  
L. EL KAIM ◽  
J. KERVAGORET ◽  
S. Z. ZARD
Keyword(s):  
Allylic Alcohols ◽  
Thermal Rearrangement ◽  
Nitro Derivatives

Preparation and Properties of Human Prothrombin Complex

1970 ◽  
Vol 24 (03/04) ◽  
pp. 325-333 ◽  
Author(s):  
G. H Tishkoff ◽  
L. C Williams ◽  
D. M Brown
Keyword(s):  
Molecular Weight ◽  
Proteolytic Enzyme ◽  
Enzyme Inhibitor ◽  
Specific Activity ◽  
Crystalline Form ◽  
Sedimentation Equilibrium ◽  
Crystalline Complex ◽  
Interaction Product ◽  
Proteolytic Enzyme Inhibitor ◽  
Purification Scheme

SummaryAs a corollary to our previous studies with bovine prothrombin, we have initiated a study of human prothrombin complex. This product has been isolated in crystalline form as a barium glycoprotein interaction product. Product yields were reduced compared to bovine product due to the increased solubility of the barium glycoprotein interaction product. On occasion the crystalline complex exhibited good yields. The specific activity of the crystalline complex was 1851 Iowa u/mg. Further purification of human prothrombin complex was made by removal of barium and by chromatography on Sephadex G-100 gels. The final product evidenced multiple procoagulant activities (II, VII, IX and X). The monomeric molecular weight determined by sedimentation equilibrium in a solvent of 6 M guanidine-HCl and 0.5% mercaptoethanol was 70,191 ± 3,057 and was homogeneous with respect to molecular weight. This product was characterized in regard to physical constants and chemical composition. In general, the molecular properties of human prothrombin complex are very similar to the comparable bovine product. In some preparations a reversible proteolytic enzyme inhibitor (p-aminophenylarsonic acid) was employed in the ultrafiltration step of the purification scheme to inhibit protein degradation.

Trypanocidal Structure-Activity Relationshipfor Cis- and Trans-methylpluviatolide

Planta Medica ◽  
2008 ◽  
Vol 74 (03) ◽  
Author(s):  
R Silva ◽  
J Saraiva ◽  
S Albuquerque ◽  
C Curti ◽  
PM Donate ◽  
...  
Keyword(s):  
Structure Activity ◽  
Cis And Trans

Active MnO2 As a Mild Oxidizing Reagent for the Controlled Oxidation of Benzylic and Allylic Alcohols

2012 ◽  
Vol 2 (6) ◽  
pp. 48-48
Author(s):  
Y. M. Nandurkar Y. M. Nandurkar ◽  
◽  
B. B. Bahule B. B. Bahule
Keyword(s):  
Allylic Alcohols

Bimetallic Radical Redox-Relay Catalysis for the Isomerization of Epoxides to Allylic Alcohols

2019 ◽  
Author(s):  
Ke-Yin Ye ◽  
Terry McCallum ◽  
Song Lin
Keyword(s):  
Ring Opening ◽  
High Reactivity ◽  
Hydrogen Atom Transfer ◽  
Organic Radicals ◽  
Epoxide Ring ◽  
Allylic Alcohols ◽  
Epoxide Ring Opening ◽  
Bond Forming ◽  
Co Catalysts ◽  
The Rich

Organic radicals are generally short-lived intermediates with exceptionally high reactivity. Strategically, achieving synthetically useful transformations mediated by organic radicals requires both efficient initiation and selective termination events. Here, we report a new catalytic strategy, namely bimetallic radical redox-relay, in the regio- and stereoselective rearrangement of epoxides to allylic alcohols. This approach exploits the rich redox chemistry of Ti and Co complexes and merges reductive epoxide ring opening (initiation) with hydrogen atom transfer (termination). Critically, upon effecting key bond-forming and -breaking events, Ti and Co catalysts undergo proton-transfer/electron-transfer with one another to achieve turnover, thus constituting a truly synergistic dual catalytic system.<br>

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