ChemInform Abstract: TERPENOIDS. XLII. A CONVENIENT STEREOSELECTIVE TRANSFORMATION OF THE 16-EXOCYCLIC METHYLENE GROUP INTO THE CARBOXY GROUP IN ENT-KAURENE AND ITS 19-OIC ACID

1978 ◽  
Vol 9 (12) ◽  
Author(s):  
E. FUJITA ◽  
M. OCHIAI
Keyword(s):  
Carboxy Group ◽  
Exocyclic Methylene ◽  
Methylene Group

scholarly journals Relation between Crystal Structures of Precursors and Final Products: Example of Vitamin D Intermediates

Molecules ◽  
2020 ◽  
Vol 25 (8) ◽  
pp. 1802
Author(s):  
Monika Wanat ◽  
Maura Malinska ◽  
Andrzej Kutner ◽  
Krzysztof Woźniak
Keyword(s):  
Vitamin D ◽  
Crystal Structures ◽  
Theoretical Calculations ◽  
Geometrical Parameters ◽  
Space Groups ◽  
Vitamin D Analogues ◽  
Vitamin D Analog ◽  
Exocyclic Methylene ◽  
Solid Form ◽  
Methylene Group

In this paper, we proved that the solid-state structure of vitamin D analog is well represented by the structures of its structural fragments. This is important in predicting the biological activity of vitamin D analogs that are not available in the solid form. The previously published crystal structure of advanced vitamin D intermediate provided additional insights into vitamin D properties. A similar analysis based on simple vitamin D intermediate analogues showed that precursors crystallized in the space groups typical for vitamins D; geometrical parameters were related to the corresponding parameters in the vitamin D analogues; and crystal structures of the basic intermediates and their final products contained similar intermolecular interactions, essential for the infinite hydrogen bond motif observed in the vitamin D analogues. The energy of these interactions is related as shown by theoretical calculations, that is, energy frameworks analysis. Moreover, analysis of the hydrogen bonds motifs revealed a relation between these motifs and the absolute configuration of basic intermediates as well as the space orientation of the exocyclic methylene group in the final structures.

THE STRUCTURE AND STEREOCHEMISTRY OF ATISINE

1964 ◽  
Vol 42 (1) ◽  
pp. 137-149 ◽  
Author(s):  
D. Dvornik ◽  
O. E. Edwards
Keyword(s):  
Long Range ◽  
Rigorous Proof ◽  
Polar Groups ◽  
Detailed Explanation ◽  
Exocyclic Methylene ◽  
Derivatives Of ◽  
Methylene Group ◽  
Absolute Stereochemistry ◽  
Basic Strength

A stereospecific hydration of the exocyclic methylene group of a derivative of the alkaloid atisine has been observed. The product was used to degrade the alkaloid to a tetracyclic phenol. This enabled rigorous proof of the structure and relative and absolute stereochemistry of atisine and related alkaloids. A detailed explanation of the abnormal basic strength and the isomerization of atisine is given. Long-range influence of polar groups on the basic strength of derivatives of the alkaloid is reported.

The stereospecific hydrogenation of an exocyclic methylene group

1966 ◽  
pp. 128 ◽  
Author(s):  
J. E. Anderson ◽  
F. G. Riddell ◽  
J. P. Fleury ◽  
J. Morgen
Keyword(s):  
Exocyclic Methylene ◽  
Methylene Group

Replacing the 2′-oxygen with an exocyclic methylene group reverses the stabilization effects of α-l-LNA

2011 ◽  
Vol 21 (1) ◽  
pp. 588-591 ◽  
Author(s):  
Punit P. Seth ◽  
Charles R. Allerson ◽  
Andres Berdeja ◽  
Eric E. Swayze
Keyword(s):  
Exocyclic Methylene ◽  
Methylene Group

Synthetic Routes to Some Isotopically Labeled Intermediates for Diterpenoid Biosynthesis

1989 ◽  
Vol 42 (4) ◽  
pp. 561 ◽  
Author(s):  
RM Dawson ◽  
IM Godfrey ◽  
RW Hogg ◽  
JR Knox
Keyword(s):  
Specific Activity ◽  
High Specific Activity ◽  
Allylic Alcohol ◽  
Isotopic Labelling ◽  
Efficient Procedure ◽  
Ene Reaction ◽  
Vinyl Bromide ◽  
Exocyclic Methylene ◽  
Synthetic Routes ◽  
Methylene Group

The exo-15-hydrogen of ent-kaurene can be exchanged through a reversible ene reaction in a convenient and efficient procedure which has the potential for giving high specific activity 3H-labelling. Copalol, the (Z)-double bond stereoisomer, and the allylic alcohol isomers ent-manool and ent-epimanool have been obtained through divergent synthetic pathways involving a 15,16-bisnor ketone intermediate. These pathways have also allowed the four compounds to be obtained with 14C-labelling. A method, involving a Wittig reaction to form a vinyl bromide intermediate, has been developed for obtaining copalol, as the trityl ether derivative, with stereospecific isotopic labelling of one or the other of the hydrogens of the exocyclic methylene group.

scholarly journals An Exocyclic Methylene Group Acts As a Bioisostere of the 2′-Oxygen Atom in LNA

2010 ◽  
Vol 132 (42) ◽  
pp. 14942-14950 ◽  
Author(s):  
Punit P. Seth ◽  
Charles R. Allerson ◽  
Andres Berdeja ◽  
Andrew Siwkowski ◽  
Pradeep S. Pallan ◽  
...  
Keyword(s):  
Oxygen Atom ◽  
Exocyclic Methylene ◽  
Methylene Group

ATISINE: THE HETEROCYCLIC RING AND FUNCTIONAL GROUPS

1954 ◽  
Vol 32 (5) ◽  
pp. 465-473 ◽  
Author(s):  
O. E. Edwards ◽  
Tara Singh
Keyword(s):  
Functional Groups ◽  
Heterocyclic Ring ◽  
Double Bonds ◽  
Secondary Hydroxyl ◽  
Exocyclic Methylene ◽  
Methylene Group ◽  
Hydroxyethyl Group

Evidence is presented which confirms the presence in atisine and isoatisine of vinylamine double bonds, an N-(β-hydroxyethyl) group, an exocyclic methylene group, and a secondary hydroxyl in an allylic relation to the latter. The size and substitution of the heterocyclic ring is discussed. The pyrolysis of atisine and isoatisine hydrochlorides to give a C20H29ON base is described.

Mechanism of formation of serine β-lactones by Mitsunobu cyclization: synthesis and use of L-serine stereospecifically labelled with deuterium at C-3

1986 ◽  
Vol 64 (4) ◽  
pp. 706-713 ◽  
Author(s):  
Shawn E. Ramer ◽  
Richard N. Moore ◽  
John C. Vederas
Keyword(s):  
Carboxy Group ◽  
Lactone Ring ◽  
Aqueous Sodium Hydroxide ◽  
Ring Closure ◽  
Protecting Groups ◽  
Hydroxy Acids ◽  
Mechanism Of Formation ◽  
Aqueous Sodium ◽  
Acylase I ◽  
Methylene Group

The ring closure of N-benzyloxycarbonyl-L-serine (1) under Mitsunobu conditions (Ph3P, dimethyl azodicarboxylate, −78 °C) to give the corresponding β-lactone (2) is shown by deuterium and oxygen-18 labelling studies to proceed by hydroxy group activation, in contrast to analogous cyclizations of more hindered β-hydroxy acids, which usually occur by carboxy group activation. Samples of 1 stereospecifically labelled with deuterium at C-3 were prepared by hydrogenation of (Z)-2-acetamido-3-methoxyacrylic acid (9) with deuterium, followed by selective Acylase I deacetylation of the 2S isomer, removal of the protecting groups, and N-acylation of the resulting L-serine with benzyl chloroformate. Mitsunobu cyclizations of this 3R deuterated N-acyl serine, of the [hydroxy-18O] analog 1g, and of the [carboxy-18O] derivative 1f show that lactonization occurs with inversion of configuration at C-3, loss of the hydroxy oxygen, and retention of the carboxy oxygens. Similar labelling experiments demonstrate that aqueous sodium hydroxide opens the β-lactone ring by exclusive attack at the carbonyl to regenerate 1, whereas acidic hydrolysis proceeds primarily by attack of water at the C-3 methylene group of 2. This information allows interconversion of L-serines that are stereospecifically labelled at C-3 with hydrogen isotopes and affords access to other labelled (β-substituted alanines.

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