Aromatic methyl group migration and hydroxylation of p-toluidine by iron-thiol and hemin-thiol systems as a model of cytochrome P-450.

1977 ◽  
Vol 25 (9) ◽  
pp. 2330-2335 ◽  
Author(s):  
HIROMU SAKURAI ◽  
MASAHIRO KITO
Keyword(s):  
Methyl Group ◽  
Group Migration ◽  
Cytochrome P 450

Thujopsene rearrangements. Ring system via methyl group migration

1972 ◽  
Vol 37 (2) ◽  
pp. 241-250 ◽  
Author(s):  
W. G. Dauben ◽  
L. E. Friedrich
Keyword(s):  
Ring System ◽  
Methyl Group ◽  
Group Migration

Methyl group migration in the preparation of o-tolyl- and p-xylyldichloroboranes

1967 ◽  
Vol 6 (11) ◽  
pp. 1975-1977 ◽  
Author(s):  
C. A. Eggers ◽  
Sidney F. A. Kettle
Keyword(s):  
Methyl Group ◽  
Group Migration

scholarly journals Conversion of 19-oxo[2β-2H]androgens into oestrogens by human placental aromatase. An unexpected stereochemical outcome

1990 ◽  
Vol 268 (3) ◽  
pp. 553-561 ◽  
Author(s):  
P A Cole ◽  
C H Robinson
Keyword(s):  
Active Site ◽  
Extended Period ◽  
Direct Role ◽  
Methyl Group ◽  
Enzyme Active Site ◽  
Model Studies ◽  
The Third ◽  
Intensive Investigation ◽  
Cytochrome P 450

Aromatase is a cytochrome P-450 enzyme that catalyzes the conversion of androgens into oestrogens via sequential oxidations at the 19-methyl group. Despite intensive investigation, the mechanism of the third step, conversion of the 19-aldehydes into oestrogens, has remained unsolved. We have previously found that a pre-enolized 19-al derivative undergoes smooth aromatization in non-enzymic model studies, but the role of enolization by the enzyme in transformations of 19-oxoandrogens has not been previously investigated. The compounds 19-oxo[2 beta-2H]testosterone and 19-oxo[2 beta-2H]androstenedione have now been synthesized. Exposure of either of these compounds to microsomal aromatase, in the absence of NADPH, for an extended period led to no significant 2H loss or epimerization at C-2, leaving open the importance of an active-site base. However, in the presence of NADPH there was an unexpected substrate-dependent difference in the stereoselectivity of H loss at C-2 in the enzyme-induced aromatization of 19-oxo[2 beta-2H]-testosterone versus 19-oxo[2 beta-2H]androstenedione. The aromatization results for 17 beta-ol derivative 19-oxo[2 beta-2H]-testosterone correspond to about 1.2:1 2 beta-H/2 alpha-H loss from unlabelled 19-oxotestosterone. In contrast, aromatization results for 19-oxo[2 beta-2H]androstenedione correspond to at least 11:1 2 beta-H/2 alpha-H loss from unlabelled 19-oxoandrostenedione. This substrate-dependent stereoselectivity implies a direct role for an enzyme active-site base in 2-H removal. Furthermore, these results argue against the proposal that 2 beta-hydroxylation is the obligatory third step in aromatase action.

Tetracyclic triterpenes. VIII. The skeletal rearrangement of 3β-acetoxy-9α,11α-epoxy-5α-lanostan-7-one: 13- and 10-methyl group migration

1985 ◽  
Vol 63 (6) ◽  
pp. 1280-1286 ◽  
Author(s):  
Zdzisław Paryzek ◽  
Roman Wydra
Keyword(s):  
Acetic Anhydride ◽  
Spectral Data ◽  
Boron Trifluoride ◽  
Boron Trifluoride Etherate ◽  
Major Product ◽  
Chemical Transformations ◽  
Skeletal Rearrangement ◽  
Methyl Group ◽  
Group Migration

The boron trifluoride etherate catalyzed rearrangement of 3β-acetoxy-9α, 11α-epoxy-5α-lanostan-7-one (1) in acetic anhydride resulted in formation of 19(10 → 9β)abeo compounds 2 and 4 along with 18(13 → 12β)abeo compound 5, as the major product. These structures are supported by spectral data and chemical transformations. The possible mechanism of the rearrangement is discussed.

scholarly journals An unexpected methyl group migration during on-column Stille derivatization of RNA

Tetrahedron ◽  
2014 ◽  
Vol 70 (2) ◽  
pp. 327-333 ◽  
Author(s):  
Lena Wicke ◽  
Joachim W. Engels
Keyword(s):  
Methyl Group ◽  
Group Migration

Synthesis of internally alkylated azuliporphyrins

2020 ◽  
Vol 24 (05n07) ◽  
pp. 817-829
Author(s):  
Julian S. D. Moriones ◽  
Alissa N. Latham ◽  
Timothy D. Lash
Keyword(s):  
Hydrochloric Acid ◽  
Alkyl Group ◽  
Acid Catalyst ◽  
Protonated Form ◽  
Free Base ◽  
Methyl Substituent ◽  
Methyl Group ◽  
Protective Groups ◽  
Group Migration ◽  
Type 3

Examples of internally alkylated azuliporphyrins were prepared by MacDonald-type “3 + 1” condensations. 2-Methyl- and 2-ethylazulene reacted with an acetoxymethylpyrrole in the presence of an acid catalyst to give azulitripyrranes. Following cleavage of the terminal protective groups, condensation with a diformylpyrrole in the presence of hydrochloric acid and oxidation with ferric chloride afforded 21-alkylazuliporphyrins. An azulene dialdehyde similarly reacted with an [Formula: see text]-methyltripyrrane to generate a 23-methylazuliporphyrin. The products could only be isolated in protonated form and the free-base internally alkylated azuliporphyrins proved to be unstable. Nevertheless, the dications are highly diatropic and the internal alkyl group resonances were shifted upfield to beyond -3 ppm. Reaction of a 23-methylazuliporphyrin with palladium(II) acetate primarily afforded a palladium(II) complex with loss of the internal methyl substituent. However, two palladium(II) benzocarbaporphyrins were also identified that were formed by sequential oxidative ring contraction and methyl group migration. Internally alkylated azuliporphyrins provide new insights into the reactivity of the system and the results show that the introduction of alkyl substituents within porphyrinoid cavities greatly modifies the properties of these structures.

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