scholarly journals On the Allylic Oxidation of Ent-kaurenic Acid Methyl Ester with Lead Tetra-acetate

2016 ◽  
Vol 11 (9) ◽  
pp. 1934578X1601100 ◽  
Author(s):  
Julio Rojas ◽  
Rosa Aparicio ◽  
Alfredo Usubillaga
Keyword(s):  
Methyl Ester ◽  
Chromic Acid ◽  
Acetic Acid Solution ◽  
Authentic Sample ◽  
Acid Methyl Ester ◽  
Flash Chromatography ◽  
Initial Compound ◽  
Pyridine Complex ◽  
Hydrolysis Of ◽  
Lead Tetra Acetate

In this paper, results obtained upon treatment of the methyl ester of ent-kaur-16-en-19-oic acid (1b) with lead tetra-acetate under reflux in glacial acetic acid solution and an argon atmosphere are described. After 30 minutes reflux, GC-MS analysis of the product indicated the presence of three substances, the initial compound (1b, 7 %), the methyl ester of ent-kaur-16-en-15- O-acetyl-19-oic acid (2a, C23H30O4, 45 %), and its isomer, the methyl ester of ent-kaur-15-en-17- O-acetyl-19-oic acid (3a, 47 %). Flash chromatography over silica gel containing 20% AgNO3 yielded 2b (456 mg), which was identified by direct comparison with an authentic sample, and 3a (472 mg), whose structure was established by uni- and bi-dimensional NMR analysis. Hydrolysis of 3a with dry ammonia in MeOH yielded the methyl ester of ent-kaur-15-en-17-hydroxy-19-oic acid (3b, C21H32O3); treatment of this compound with chromic acid/pyridine complex rendered the aldehyde (4).

BROMINATION OF STEROID 20-KETALS

1959 ◽  
Vol 37 (2) ◽  
pp. 345-350 ◽  
Author(s):  
Arthur A. Amos ◽  
P. Ziegler
Keyword(s):  
Methyl Ester ◽  
Acid Hydrolysis ◽  
Good Yield ◽  
Acid Methyl Ester ◽  
Acid Methyl ◽  
Hydrolysis Of

Bromination of 3α,12α-diacetoxypregnan-20-one ethylene ketal provided in good yield the corresponding 21-monobromo compound. This product, on acid hydrolysis and subsequent acetolysis, gave the known 3α,12α,21-triacetoxypregnan-20-one. Acid hydrolysis of the bromoketal, followed by Faworsky rearrangement, led to 3α,12α-diacetoxy-17α-methyletiocholanic acid methyl ester.

Separation and characterization of 61- and 57-kDa lipases from Geotrichum candidum ATCC 66592

1992 ◽  
Vol 38 (1) ◽  
pp. 75-80 ◽  
Author(s):  
Tomas Jacobsen ◽  
Otto M. Poulsen
Keyword(s):  
Oleic Acid ◽  
Methyl Ester ◽  
Palmitic Acid ◽  
Initial Velocity ◽  
Acid Methyl Ester ◽  
Geotrichum Candidum ◽  
Acid Methyl ◽  
Oleic Acid Methyl Ester ◽  
Palmitic Acid Methyl Ester ◽  
Hydrolysis Of

Two lipolytic proteins (61 and 57 kDa) present in a Sephadex G-100 fraction of extracellular lipase from Geotrichum candidum ATCC 66592 were separated using high-performance liquid chromatography. Crossed electrofocusing immunoelectrophoresis was used to demonstrate that the 61-kDa lipase fraction contained two forms of lipase with pI 4.5 and 4.7. However, when deglycosylated with endoglycosidase H, the two forms gained an identical pI, 4.6. The 57-kDa lipase fraction contained one form of lipase with pI close to 4.5. Although the 61- and 57-kDa lipases were immunologically identical, the substrate specificity differed. Thus, the 61-kDa lipase hydrolysed palmitic acid methyl ester at an initial velocity of hydrolysis that was 60% of the initial velocity of hydrolysis of oleic acid methyl ester, whereas the 57-kDa lipase hydrolysed palmitic acid methyl ester at an initial velocity of hydrolysis that was only7% of the initial velocity of hydrolysis of oleic acid methyl ester. Key words: Geotrichum candidum, lipases, multiple forms, deglycosylation, substrate specificity.

A synthesis of (−)-deoxypodocarpic acid methyl ester via an enzymatic enantioselective hydrolysis of the key intermidiate enol ester

Tetrahedron ◽  
1989 ◽  
Vol 45 (19) ◽  
pp. 6135-6144 ◽  
Author(s):  
Takeshi Sugai ◽  
Hideaki Kakeya ◽  
Hiromichi Ohta ◽  
Mitsuo Morooka ◽  
Shigeru Ohba
Keyword(s):  
Methyl Ester ◽  
Acid Methyl Ester ◽  
Enantioselective Hydrolysis ◽  
Acid Methyl ◽  
Hydrolysis Of ◽  
Enol Ester
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