Synthesis of Lambertianic Acid

1972 ◽  
Vol 50 (23) ◽  
pp. 3749-3760 ◽  
Author(s):  
R. A. Bell ◽  
M. B. Gravestock ◽  
V. Y. Taguchi
Keyword(s):  
Oxygen Atom ◽  
Acid Chloride ◽  
Liquid Ammonia ◽  
Furan Ring ◽  
Nucleophilic Attack ◽  
Reformatsky Reaction ◽  
Lambertianic Acid ◽  
Exocyclic Methylene ◽  
Methylene Group

A synthesis of lamberlianic acid 2a starting from podocarpic acid is described. The central intermediate, diester-ketone 4b, is obtained by ozonolysis and hydrogenation, and the exocyclic methylene group in ring B generated via a Reformatsky reaction. The furan ring is attached by nucleophilic attack of 3-lithiofuran, for which an improved preparation is described, on either the acid chloride 7b or the aldehyde 16. The 12-oxygen atom is removed by mesylation of the alcohols 12a and b and Li–liquid ammonia reduction.

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

Darstellung und Kristallstruktur von Lithiumozonid-Ammoniakat (1/5) LiO3 · 5 NH3/Synthesis and Crystal Structure of Lithiumozonide-Ammonia (1/5) LiO3 · 5 NH3

1999 ◽  
Vol 54 (11) ◽  
pp. 1345-1349 ◽  
Author(s):  
Wilhelm Klein ◽  
Martin Jansen
Keyword(s):  
Crystal Structure ◽  
Oxygen Atom ◽  
Cation Exchange ◽  
Liquid Ammonia ◽  
Boiling Temperature ◽  
Synthesis And Crystal Structure ◽  
Central Oxygen

Lithium ozonide has been synthezised starting from cesium ozonide via cation exchange in liquid ammonia and crystallizes at -78°C as an ammoniate, LiO3 · 5NH3. The coarse, ruby red crystals decompose above the boiling temperature of ammonia and are extremely sensitive to moisture. The crystal structure of L iO3 · 5NH3 (P c21n; a = 1231.9(5), b = 637.4(2), c = 1104.8(4) pm; Z = 4; R1 = 4.57%; 1318 independent reflections) consists of lithium tetramine complexes, ozonide anions and non coordinating ammonia molecules. With respect to the arrangement of the complex cations and of the anions there is similarity to the WC type of structure. The central oxygen atom of the ozonide anion is disordered.

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.

Diyne Cyclization in Camphor Derivatives - Experimental and Theoretical Investigation

1996 ◽  
Vol 51 (11) ◽  
pp. 1655-1662 ◽  
Author(s):  
Gabriele Wagner ◽  
Christian Heiß ◽  
Uwe Verfiirth ◽  
Rudolf Herrmann
Keyword(s):  
Oxygen Atom ◽  
Theoretical Investigation ◽  
Positive Charge ◽  
Membered Ring ◽  
Titanium Chloride ◽  
Nmr Studies ◽  
Methylene Carbon ◽  
Camphor Derivatives ◽  
Exocyclic Methylene ◽  
Derivatives Of

Derivatives of 3-oxo-camphorsulfonimide (1) with two phenylethynyl groups in the endo positions at the carbons C-2 and C-3 were prepared, and their reactivity towards halogenes and titanium chloride was studied. In every case, the two ethynyl groups led to the annulation of a five-membered ring to the bicyclo[2 .2 .1] system in an orientation which depends on the bulkiness of the additional substituent in position 3. NMR studies show that cationic species like 6 and 8 are the first detectable intermediates. They not only contain the fused five-membered ring but also a bond between its exocyclic methylene carbon and an oxygen atom of the sulfonyl group, thus transferring the positive charge mainly to sulfur. Semiempirical calculations (PM3) suggest two intermediates in the formation of such cations.

scholarly journals Off-pathway 3D-structure provides protection against spontaneous Asn/Asp isomerization: shielding proteins Achilles heel

2020 ◽  
Vol 53 ◽  
Author(s):  
András Láng ◽  
Imre Jákli ◽  
Kata Nóra Enyedi ◽  
Gábor Mező ◽  
Dóra K. Menyhárd ◽  
...  
Keyword(s):  
Protective Factor ◽  
Structural Integrity ◽  
3D Structure ◽  
Nucleophilic Attack ◽  
Structural Element ◽  
Backbone Conformation ◽  
Peptide Models ◽  
Geometric Descriptors ◽  
Restricted Mobility ◽  
Methylene Group

Abstract Spontaneous deamidation prompted backbone isomerization of Asn/Asp residues resulting in – most cases – the insertion of an extra methylene group into the backbone poses a threat to the structural integrity of proteins. Here we present a systematical analysis of how temperature, pH, presence of charged residues, but most importantly backbone conformation and dynamics affect isomerization rates as determined by nuclear magnetic resonance in the case of designed peptide-models. We demonstrate that restricted mobility (such as being part of a secondary structural element) may safeguard against isomerization, but this protective factor is most effective in the case of off-pathway folds which can slow the reaction by several magnitudes compared to their on-pathway counterparts. We show that the geometric descriptors of the initial nucleophilic attack of the isomerization can be used to classify local conformation and contribute to the design of stable protein drugs, antibodies or the assessment of the severity of mutations.

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

scholarly journals An adenosine triphosphate-dependent carbamoylphosphate-3-hydroxymethylcephem O-carbamoyltransferase from Streptomyces clavuligerus

1980 ◽  
Vol 185 (3) ◽  
pp. 555-564 ◽  
Author(s):  
S J Brewer ◽  
P M Taylor ◽  
M K Turner
Keyword(s):  
Carboxylic Acid ◽  
Oxygen Atom ◽  
Deae Cellulose ◽  
Streptomyces Clavuligerus ◽  
Wide Range ◽  
Nucleoside Triphosphates ◽  
Phosphate Anions ◽  
Beta 2 ◽  
Methylene Group ◽  
Carbamoyl Group

Cell-free supernatants from cells of Streptomyces clavuligerus (N.R.R.L. 3585), which are actively synthesizing cephamycin C, transfer a carbamoyl group from carbamoylphosphate to a 3-hydroxymethylceph-3-em-4-carboxylic acid nucleus to form a 3-carbamoyloxymethylcephem. This reaction was stimulated by nucleoside triphosphates and by a mixture of Mn2+ and Mg2+ cations. The enzyme responsible was purified 40-fold by batch absorption onto DEAE-cellulose and hydroxyapatite. The purified O-carbamoyltransferase is most active at pH 6.8. It is stabilized by phosphate anions, but is inhibited by PPi anions, (NH4)2SO4 or NaCl. The enzyme is stimulated by ATP, but it is not known whether this nucleotide acts as an effector or as a substrate. Some activity is observed with dATP, but two other analogues of ATP, in which a methylene group replaced the oxygen atom between the alpha- and beta- or the beta- and gamma-phosphorus atoms, inhibit the action of ATP itself. The enzyme synthesizes a wide range of 3-carbamoyloxymethylcephems. The structure of some of these products, for example that of cefuroxime (3-carbamoyloxymethyl-7 beta-[2-(fur-2-yl)-2-syn-methoxyiminoacetamido]ceph-3-em-4-carboxylic acid), was confirmed by their proton-n.m.r. spectra.

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
Sign in / Sign up

Export Citation Format

Share Document