Elimination reaction of angular hydroxymethyl groups of 20(29)-lupene derivatives

1983 ◽  
Vol 48 (5) ◽  
pp. 1499-1507 ◽  
Author(s):  
Alois Vystrčil ◽  
Václav Křeček ◽  
Miloš Buděšínský
Keyword(s):  
Double Bond ◽  
Catalytic Reduction ◽  
Cotton Effect ◽  
Membered Ring ◽  
Side Chain ◽  
Elimination Reaction ◽  
Conjugated Diene ◽  
Trisubstituted Double Bond ◽  
Diene System ◽  
Dibromo Derivative

Solvolysis of 28-p-toluenesulfonyloxy-20(29)-lupene derivatives IV-VII proceeds with isomerization of the isopropenyl side chain to the isopropylidene chain and expansion of the ring E to a six-membered ring, containing trisubstituted double bond; for „anhydrobetulin" and its derivatives formulae VIII-XI with homoconjugated double bonds are suggested. Formation of a conjugated diene system is hindered by steric interactions of the isopropylidene chain with the ring C (with C(12)). Only the trisubstituted double bond in the dienes VIII and X undergoes catalytic reduction, the hydrogen approaching from the α-side (XII-XVI) as demonstrated by the Cotton effect of trinorketone XXI and its 20,20-dibromo derivative XXIII.

scholarly journals Structures and apoprotein linkages of phycoerythrobilin and phycocyanobilin

1980 ◽  
Vol 187 (2) ◽  
pp. 311-320 ◽  
Author(s):  
S. Derek Killilea ◽  
Padraig O'Carra ◽  
Richard F. Murphy
Keyword(s):  
Double Bond ◽  
Pyrrole Ring ◽  
Cysteine Residue ◽  
Side Chain ◽  
Elimination Reaction ◽  
Serine Residue ◽  
Structural Revision ◽  
Carbon Side Chain ◽  
Outer Position ◽  
Reduced State

Phycoerythrobilin and phycocyanobilin are covalently attached to the apoproteins of phycoerythrins and phycocyanins. One linkage consists of an ester bond between the hydroxy group of a serine residue and the propionate side chain on one of the inner pyrrole rings (probably ring C). The other linkage is a labile thioether bond between a cysteine residue and the two-carbon side chain on pyrrole ring A. This side chain and both of the α-positions of the ring A are in the reduced state. This constitutes an important structural revision, since, in the structures currently accepted for the phycobilins, the two-carbon side chain on ring A is depicted as an ethylidene grouping and this has been regarded not only as a very characteristic feature of the phycobilins, but also as a probable structural feature of the chromophore of phytochrome, largely on the basis of other analogies with the phycobilins. The ethylidene-containing structures apply instead to artefact forms of the pigments released from the apoproteins by treatment with hot methanol. Cleavage of the ring-A linkage involves an elimination reaction releasing the cysteine residue and generating a double bond in the ring-A side chain. During cleavage in methanol the direction of the elimination is towards the ring, generating the ethylidene double bond. Since this is linked to the conjugated system, the methanol-released pigments differ spectrally from the native phycobilins. During acid-catalysed release of the pigments, the elimination apparently goes in the opposite direction, generating a double bond at the outer position of the side chain. Since this double bond is not linked to the conjugated system, the acid-released pigments remain spectrally identical with their protein-bound counterparts.

A Novel Scheme for the Synthesis of 21-Acetoxypregna-1,4,9(11)-triene- 17α,21-diol-3,20-dione from 9α-Hydroxyandrostenedione

2020 ◽  
Vol 16 (5) ◽  
pp. 606-610
Author(s):  
Nguyen T. Diep ◽  
Luu D. Huy
Keyword(s):  
Double Bond ◽  
Chemical Synthesis ◽  
Economic Efficiency ◽  
Final Stage ◽  
Side Chain ◽  
Entire Process ◽  
Drug Synthesis ◽  
First Time

Background: Vietnam currently imports up to 90% of the pharmaceuticals it consumes and 100% of the steroid-based pharmaceuticals. The ability for efficient chemical synthesis of the steroids could create commercial opportunities to address this issue. Synthesis of 21-acetoxypregna-1,4,9(11)- triene-17α,21-diol-3,20-dione is considered a key intermediate in the scheme of steroidal drug synthesis. Previous synthesis attempts of such steroids (corticoids) introduce a double bond at C-1(2) in the final stage of synthesis, which delivers a poor yield and reduces the economic efficiency of the process. Objective: To study and develop a novel and effective method for the synthesis of 21-acetoxypregna- 1,4,9(11)-triene-17α,21-diol-3,20-dione. Methods: Using 9α-hydroxyandrostenedione as a substrate chemical synthesis was performed as follows: pregnane side chain construction at C-17 (acetylene method), introduction of C-1(2) double bond (using SeO2), epimerization of C-17 (via 17-ONO2 ester) and Stork’s iodination. Results: 21-acetoxypregna-1,4,9(11)-triene-17α,21-diol-3,20-dione was prepared from 9α- hydroxyandrostenedione with an improved yield compared to previous attempts. Conclusion: Here, 21-acetoxypregna-1,4,9(11)-triene-17α,21-diol-3,20-dione has been synthesized from 9α-hydroxyandrostenedione based on a novel, effective and commercially feasible scheme. The introduction of the C-1(2) double bond at an earlier stage of the synthesis has increased the economic efficiency of the entire process. For the first time, the indirect epimerization mechanism has been clarified along with the configuration of the C-17 stereo-center which has been confirmed using NOESY data.

Nonconventional electrophilic heteroaromatic substitutions: ring vs. side-chain reactivity of 2,5-dimethyl five-membered ring heterocycles toward electron-deficient aromatics

1984 ◽  
Vol 49 (23) ◽  
pp. 4363-4367 ◽  
Author(s):  
Francois Terrier ◽  
Jean Claude Halle ◽  
Marie Paule Simonnin ◽  
Marie Jose Pouet
Keyword(s):  
Membered Ring ◽  
Side Chain

Critical Review of Biotransformational Studies on Steroids by Using Culture of Cunninghamella blakesleeana

2021 ◽  
Vol 18 ◽  
Author(s):  
Azizuddin ◽  
Muhammad Iqbal ◽  
Syed Ghulam Musharraf
Keyword(s):  
Double Bond ◽  
Critical Review ◽  
Structural Modification ◽  
Bond Formation ◽  
Environmentally Friendly ◽  
Side Chain ◽  
Synthetic Compounds ◽  
Efficient Approach ◽  
Cunninghamella Blakesleeana ◽  
Different Strains

: For several decades, biotransformational studies on steroidal compounds have gained a lot of attention because it is an efficient approach for the structural modification of complicated natural or synthetic compounds with high regio-, chemo- and stereoselectivity at environmentally friendly conditions. This review summarizes the use of different strains of Cunninghamella blakesleeana for the biotransformation of sixteen steroids 1-16 into a variety of transformed products. The transformed products may be important as a drug or precursor for the production of important pharmaceuticals. The types of reactions performed by C. blakesleeana include hydroxylation, epoxidation, reduction, demethylation, oxidation, glycosidation, double bond formation, side-chain degradation, isomerisation and opening of an isoxazol ring, which would be difficult to produce by traditional synthesis.

scholarly journals Iodine(III)-mediated halogenations of acyclic monoterpenoids

2018 ◽  
Vol 14 ◽  
pp. 1103-1111 ◽  
Author(s):  
Laure Peilleron ◽  
Tatyana D Grayfer ◽  
Joëlle Dubois ◽  
Robert H Dodd ◽  
Kevin Cariou
Keyword(s):  
Double Bond ◽  
Hypervalent Iodine ◽  
Halide Salt ◽  
Trisubstituted Double Bond ◽  
Excellent Selectivity

Five different halofunctionalizations of acyclic monoterpenoids were performed using a combination of a hypervalent iodine(III) reagent and a halide salt. In this manner, the dibromination, the bromo(trifluoro)acetoxylation, the bromohydroxylation, the iodo(trifluoro)acetoxylation or the ene-type chlorination of the distal trisubstituted double bond occurred with excellent selectivity and moderate to good yields.

Migration of the Double Bond in the Side Chain of Sterols with Iodine.

1970 ◽  
Vol 35 (12) ◽  
pp. 4145-4148 ◽  
Author(s):  
Nobuo Ikekawa ◽  
Yasushi Honma ◽  
Naoko Morisaki ◽  
Kiyoshi Sakai
Keyword(s):  
Double Bond ◽  
Side Chain

The Influence of the Aromatic Amino Acid Side-Chains on the Sign of the Soret Cotton Effect in Chironomus Hemoglobin (CTT III)

1972 ◽  
Vol 27 (5) ◽  
pp. 530-532 ◽  
Author(s):  
Jörg Fleischhauer ◽  
Axel Wollmer
Keyword(s):  
Amino Acid ◽  
Aromatic Amino Acid ◽  
Cotton Effect ◽  
Side Chain ◽  
Side Chains ◽  
Aromatic Side Chain ◽  
Rotational Strength ◽  
Amino Acid Side Chains ◽  
Atomic Coordinates

The origin of the positive Soret Cotton effect of myoglobin was calculated by Hsu and WOODY on the basis of a mechanism taking into account the coupling of the Soret and aromatic side-chain π—π* transitions. HUBER and coworkers have worked out the atomic coordinates of a monomeric insect hemoglobin which exhibits a negative Soret Cotton effect.It seemed of some importance to examine the capability of this mechanism to explain the observed inversion of sign. The calculations resulted indeed in a negative total rotational strength (—0,2 DBM), the main contributions arising from phenylalanine residues.

Additionen an die Si=N-Doppelbindung – Kristallstruktur eines (SiNCO)-Vierringes / Additions to the Si=N-Double Bond - Crystal Structure of a (SiNCO)-Four Membered Ring

1991 ◽  
Vol 46 (6) ◽  
pp. 709-713 ◽  
Author(s):  
Susanne Vollbrecht ◽  
Uwe Klingebiel ◽  
Dieter Schmidt-Bäse
Keyword(s):  
Crystal Structure ◽  
Double Bond ◽  
Single Crystals ◽  
Membered Ring ◽  
Thermal Cleavage

In the reaction with benzophenone and phenylaldehyde lithiated aminofluorosilanes behave like iminosilanes. Four membered rings are formed in (2+2) cycloadditions. The oxaazasilacyclobutane ((CMe3)2Si—NCMe3—C6H5CH—O—) was purified by destillation. Single crystals were obtained by recrystallization from hexane. The thermal cleavage of the (SiNCO)-rings leads to carboimines and cyclosiloxanes. The lithium derivate of di-tert-butylfluorosilyl-2.6-diisopropylphenylamine reacts with 2-methyl-propenal-2 in two competing ways. In a (2+4) cycloaddition an 1-oxa-3-aza-2-sila-5-cyclohexene is formed, and in a (2+2) cycloaddition 2-methyl-2-propenyl-N-(2.6-diisopropylphenyl)imine is generated via an (SiNCO)-ring intermediate.

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