3981-83-7Relevant articles and documents
Synthesis of nucleoside analogues using acyclic diastereoselective reactions
Lussier, Tommy,Waltz, Marie-Eve,Freure, Garrett,Mochirian, Philippe,Dostie, Starr,Prévost, Michel,Guindon, Yvan
, p. 113 - 142 (2019)
The design of novel xylo-like nucleoside analogues bearing a C3’ all-carbon quaternary center and a C2’-hydroxy substituent is described. Synthesis of this scaffold makes use of highly diastereoselective transformations on acyclic substrates. Central to the approach is formation of a 2,4-syn cyanohydrin from cyanide addition onto an aldehyde through a proposed seven-membered ring chelate using a bidentate Lewis acid. In addition, a highly diastereoselective Mukaiyama aldol reaction, an intramolecular radical atom cyclization, and thioaminal formation are used to generate this novel molecule. A series of related nucleoside analogues are being tested as antiviral and anticancer agents.
Multidentate Lewis acids. Adducts of monodentate and bidentate titanium trichloroalkoxides with ketones
Bachand, Benoit,Wuest, James D.
, p. 2015 - 2025 (1991)
Like TiCl4, titanium trichloroisopropoxide (4) is a strong Lewis acid able to form 1:2 adducts with ketones. Low-temperature 1H and 13C NMR spectra indicate that these adducts adopt a mer octahedral geometry. Exchange of free and bound pinacolone occurs by a dissociative mechanism with ΔG?219 = 9.2 kcal/mol. Potentially bidentate titanium trichloroalkoxides 19-21 can be prepared by treating the bis(trimethylsilyl) ethers of trans-1,2-cyclohexanediols with 2 equiv of TiCl4. Compounds 19-21 form crystalline 1:2 ketone adducts even in the presence of excess ketone. An X-ray crystallographic study has shown that the close proximity of the OTiCl3 groups favors symmetric adducts 30 (X = Cl) with bridging chlorides, not adducts 31 with bridging, doubly activated carbonyl groups. Similar chloride-bridged structures are adopted in solution. Low-temperature 1H and 13C NMR spectra establish that unsymmetric 1:3 adducts 36 (X = Cl) are formed in solution in the presence of additional ketone. Symmetrization of the 1:3 pinacolone complex derived from bidentate titanium trichloroalkoxide 21 occurs by a normal dissociative mechanism with ΔG?223 = 10.4 kcal/mol. Since this process is slower than exchange in 1:2 adducts of monodentate analogue 4, symmetric intermediates or transition states 38 (X = Cl) with a single bridging carbonyl oxygen do not offer a low-energy intramolecular pathway for exchange. Slow exchange in the 1:3 adduct provides evidence that the two OTiCl3 groups in compounds 19-21 cooperate by forming a single chloride bridge that enhances the Lewis acidity of one site at the expense of the other.
Total synthesis of the actinoallolides and a designed photoaffinity probe for target identification
Anketell, Matthew J.,Paterson, Ian,Sharrock, Theodore M.
supporting information, p. 8109 - 8118 (2020/11/03)
The actinoallolides are a family of polyketide natural products isolated from the bacterium Actinoallomurus fulvus. They show potent biological activity against trypanosomes, the causative agents of the neglected tropical diseases human African trypanosomiasis (sleeping sickness) and Chagas disease, while exhibiting no cytotoxicity against human cell lines. Herein, we give a full account of our strategy evolution towards the synthesis of this structurally unique class of 12-membered macrolides, which culminated in the first total synthesis of (+)-actinoallolide A in 20 steps and 8% overall yield. Subsequent late-stage diversification then provided ready access to the congeneric (+)-actinoallolides B-E. Enabled by this flexible and efficient endgame sequence, we also describe the design and synthesis of a photoaffinity probe based on actinoallolide A to investigate its biological mode of action. This will allow ongoing labelling studies to identify their protein binding target(s). This journal is
Enantioselective total synthesis of (+)-reserpine
Rajapaksa, Naomi S.,McGowan, Meredeth A.,Rienzo, Matthew,Jacobsen, Eric N.
supporting information, p. 706 - 709 (2013/04/10)
A catalytic, enantioselective synthesis of (+)-reserpine is reported. The route features a highly diastereoselective, chiral catalyst-controlled formal aza-Diels-Alder reaction between a 6-methoxytryptamine-derived dihydro-β-carboline and an enantioenriched α-substituted enone to form a key tetracyclic intermediate. This approach addresses the challenge of setting the C3 stereogenic center by using catalyst control. Elaboration of the tetracycle to (+)-reserpine includes an intramolecular aldol cyclization and a highly diastereoselective hydrogenation of a sterically hindered enoate.
Stereoselective titanium-mediated aldol reactions of α-benzyloxy methyl ketones
Pellicena, Miquel,Solsona, Joan G.,Romea, Pedro,Urpi, Felix
, p. 10338 - 10350,13 (2012/12/12)
Good levels of 1,4-anti asymmetric induction are obtained in the TiCl 3(i-PrO)-mediated aldol reaction of chiral α-benzyloxy methyl ketones with a wide array of aldehydes. This methodology represents a new approach to substrate-controlled acetate aldol reactions capable of providing highly functionalized fragments in a straightforward manner, which may be useful in the design of more efficient syntheses.
Stereoselective titanium-mediated aldol reactions of α-benzyloxy methyl ketones
Pellicena, Miquel,Solsona, Joan G.,Romea, Pedro,Urpí, Fèlix
, p. 10338 - 10350 (2013/01/15)
Good levels of 1,4-anti asymmetric induction are obtained in the TiCl 3(i-PrO)-mediated aldol reaction of chiral α-benzyloxy methyl ketones with a wide array of aldehydes. This methodology represents a new approach to substrate-controlled acetate aldol reactions capable of providing highly functionalized fragments in a straightforward manner, which may be useful in the design of more efficient syntheses.
METHOD OF PRODUCING (3R,4S)-L-(4-FLUOROPHENYL)-3-[(3S)-3-(4-FLUOROPHENYL)- HYDROXYPROPYL)]-4-(4-HYDROXYPHENYL)-2-AZETIDINONE
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Page/Page column 16, (2009/12/27)
Method of producing (3R,4S)-l-(4-fiuorophenyl)-3-[(3S)-3-(4-fluorophenyl)-3- hydroxypropyl)]-4-(4-hydroxyphenyl)-2-azetidinone (ezetimibe) of formula I, in which alcohol-oxazolidide of general formula II, wherein PG is a phenol protecting group, such as a carbonate group, for instance benzyloxycarbonyl or tert-butyloxycarbonyl, or an arylmethyl group, for instance benzyl, benzhydryl or trityl, or a silyl group, for instance tert- butyldimethylsilyl or thexyldimethylsilyl, is silylated by silylation agents in an inert organic solvent in the temperature range of -10 0C to the boiling temperature of the mixture; the obtained silylether-oxazolidide of general formula III, wherein PG is as defined above and X is a silyl group of general formula SiR1R2R3, wherein R1 to R3 are identical or different alkyl groups with 1 to 5 carbon atoms or the phenyl group, is cyclized by action of bis(trimethylsilyl)acetamide and a base in an inert organic solvent in the temperature range of -20 to 40 0C; and, finally, the obtained protected azetidinone of general formula IV, wherein PG is as defined above and Y is hydrogen or the group X as defined above, is deprotected by action of deprotecting hydrogenolytic agents and/or acidic agents in an inert organic solvent.
INTERMEDIATES FOR THE PREPARATION OF (3R, 4S) -1- (4-FLUOROPHENYL) -3- [ (3S) -3- (4-FLUOROPHENYL) -3-HYDROXYPROPYL) ] -4- (4-HYDROXYPHENYL) -2-AZETIDINONE
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Page/Page column 10, (2009/10/21)
A method for the preparation of (S)-alcohol oxazolidides of general formula II, in which PG represents hydrogen or a hydroxyl protecting group, such as trimethylsilyl, tert-butyldimethylsilyl, benzyloxycarbonyl, tert-butoxycarbonyl, benzyl, benzhydryl or trityl, in which a ketal oxazolidide of general formula III, where PG has the same meaning as above and R means an alkyl with 1-4 carbon atoms, linear or branched, such as methyl, ethyl, isopropyl or butyl, or R+R together represents a divalent alkyl, or substituted with 1 or 2 alkyl groups, e.g. 1,2-ethylene, 1,2-propylene, 1,2-butylene, 1,3-propylene or 2,2-dimethyl-l,3- propylene, is deprotected by the action of acidic reagents in a mixture of water and a water- miscible solvent in the temperature range of 0 to 100 °C (stage A), and the obtained ketone oxazolidide of general IV, in which PG has the same meaning as above, is reduced with asymmetrical reagents in an inert organic solvent in the temperature range of -30 to +40 °C (stage B).
PROCESS FOR THE PRODUCTION OF EZETIMIBE AND INTERMEDIATES USED IN THIS PROCES
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Page/Page column 17, (2008/06/13)
This invention provides a novel, industrially easily realizable and economical process comprising only few steps, and built on new intermediates for the production of 1-(4-3(R)- [3(S)-(4-fluorophenyl)-3-hydroxypropyl]-4(S)-(4-hydroxyphenyl)-2-azetidinone (ezetimibe) according to the following reaction scheme: (I), (II), (III), (IV), (V), (VI), (VII), (VIII), (IX), (X), (XI) wherein, the substances of the general Formulas II, IV, VI, VIII, IX, X and XI are new, Formula III is a non-isolated intermediate, Rl, R2 and R3 are represented by the compounds of Formulas Va-Vd, (Va), (Vb), (Vc), (Vd) and R4 is a silil, e.g. tert.buthyl-dimethyl-silil, tert-buthyl-diphenyl-silil group.
SYNTHESIS OF CYCLOPENTENONES
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Page/Page column 6-7, (2008/06/13)
The invention relates to a process for the preparation, in a single step, of substituted 2-cyclopenten-l-ones by reacting a substituted enone with an aldehyde in the presence of a catalytic system. Said catalytic system consists of a metal complex, such as a [Ti(Cl)3(alkoxy)], and a co-ingredient, such as a carboxylic acid anhydride or an anhydrous salt.
