RESUMO
Aldosterone 1 is a mineralocorticoid, it has great influence on the blood pressure and its glucuronide is an important marker for the detection of several diseases. Here, we describe the chemical synthesis of different aldosterone-18- and 20-glucuronides. Reaction of trimethylsilyl 2,3,4-tri- acetyl-1-ß-glucuronic acid methyl ester 5 b and aldosterone diacetate 11 in the presence of TMSOTf gave the 18-α-glucuronide 9 a. The 18-ß-glucuronide 15 b and the 20-ß-glucuronide 16 b could be obtained by reaction of methyl 2,3,4-tri-O-isobutyryl-1α-glucuronate trichloroacetimidate 14 and aldosterone 21-acetate 8 in the presence of TMSOTf or BF3 â OEt2 . Finally, reaction of aldosterone 21-acetate 8 and methyl 2,3,4-triacetyl-1α-glucuronate trichloroacetimidate 19 in the presence of TMSOTf gave the corresponding methyl 18-ß-triacetylglucuronate 9 b, which was transformed into the desired aldosterone-18-ß-glucuronide 3 by two enzyma- tic transformations.
Assuntos
Aldosterona , Glucuronídeos , Aldosterona/análogos & derivados , Aldosterona/síntese química , Aldosterona/química , Biomarcadores/química , Fenômenos Químicos , Glucuronatos/química , Glucuronídeos/síntese química , Glucuronídeos/químicaRESUMO
A one pot borylation/Suzuki-Miyaura reaction of the 4-bromochromanone lactones 21 and 23, respectively, followed by cleavage of the methyl ether moieties gave the homodimeric chromanone lactones 10 and 11. Reaction of a 1:1 mixture of 21 and 23 under otherwise identical conditions gave a 1:1:2-mixture of the two homodimers 10 and 11 and the heterodimer 12. This is the first example of the preparation of a heterodimeric chromanone lactone. For the enantioselective synthesis of the starting material, phenol 17 was transformed into the chromane 18 using a Wacker-type cyclisation with 99 % ee and 80 % yield.
RESUMO
This work reports on the enantioselective total synthesis of the two dimeric natural chromanone lactones phomopsis-H76â A (5) and blennolideâ H (6). Both syntheses could be achieved from chromane 11, which was obtained by an enantioselective Wacker-type cyclization with >99 % ee. The dimerization of the corresponding monomers was performed using a palladium-catalyzed Suzuki reaction. Moreover, within this work it was possible to revise the absolute configuration of phomopsis-H76â A and determine the relative as well as absolute configuration of blennolideâ H.
RESUMO
An enantioselective total synthesis of blennolide D and the enantiomers of blennolide E and F is described using an enantioselective Wacker-type oxidation followed by the formation of the lactone moiety. For the introduction of the hydroxyl group in the γ-lactone, a TEMPO-mediated α-oxygenation was used which was followed by a benzylic oxidation and deprotection to give the desired compounds. In addition, an unknown diastereomer was synthesized.
RESUMO
An efficient one-pot method for the stereoselective synthesis of novel iminosugar C-nitromethyl glycosides is described. This new class of iminosugar glycosides has versatile nitromethyl functionality whose utility was further demonstrated in the single-step synthesis of bicyclic iminosugars. Under reagent-free conditions, the N-allyl-C-nitromethyl glycosides resulted in intramolecular cyclization to iminosugar-oximes, whereas under SET oxidation, they furnished cyclopropane-fused iminosugars. The N-propargyl-C-nitromethyl glycosides underwent an unprecedented ketenimine-acrylamidine-Michael addition cascade reaction to give bicyclic amidines.
RESUMO
The first enantioselective total synthesis of natural dicerandrolâ C (1 c) as its enantiomer containing a dimeric tetrahydroxanthenone skeleton is described starting from the enantiopure chromane 6 which was obtained through a Wacker-type cyclization with >99 % ee. For the formation of the dimeric skeleton a palladium-catalyzed Suzuki reaction was used. The synthesis allowed the confirmation of the absolute configuration of the dicerandrols.
Assuntos
Xantonas/química , Xantonas/síntese química , Catálise , Ciclização , Dimerização , Paládio/química , Estereoisomerismo , Xantenos/químicaRESUMO
A facile and convergent approach has been developed for the stereoselective construction of biologically important polyhydroxylated 2-acyl indolizidine framework using aza-Cope rearrangement-Mannich cyclization as a key step. The generality of this methodology is demonstrated with various lactol-tosylates derived from carbohydrates. The presented method provides an easy access to indolizidine- and tetrahydroindolizine-based iminosugar derivatives in good yields.
Assuntos
Indolizidinas/química , Antineoplásicos/síntese química , Antineoplásicos/química , Compostos Aza/química , Carboidratos/química , Cristalografia por Raios X , Ciclização , Indolizidinas/síntese química , Conformação Molecular , EstereoisomerismoRESUMO
Direct oxidation of the 4,6-O-benzylidene acetal protecting group to C-6 carboxylic acid has been developed that provides an easy access to a wide range of biologically important and synthetically challenging uronic acid and sugar amino acid derivatives in good yields. The RuCl3 -NaIO4 -mediated oxidative cleavage method eliminates protection and deprotection steps and the reaction takes place under mild conditions. The dual role of the benzylidene acetal, as a protecting group and source of carboxylic acid, was exploited in the efficient synthesis of six-carbon sialic acid analogues and disaccharides bearing uronic acids, including glycosaminoglycan analogues.
Assuntos
Acetais/química , Aminoácidos/síntese química , Amino Açúcares/síntese química , Compostos de Benzilideno/química , Ácidos Carboxílicos/química , Glicosaminoglicanos/química , Glicosaminoglicanos/síntese química , Ácidos Urônicos/síntese química , Aminoácidos/química , Amino Açúcares/química , Estrutura Molecular , Oxirredução , Estereoisomerismo , Ácidos Urônicos/químicaRESUMO
A mild and efficient one-pot method has been developed for the stereoselective synthesis of structurally diverse novel iminosugar C-alkynylglycosides. The generality of this methodology has been demonstrated with a wide variety of amines and copper acetylides. This one-pot method has been exploited in the synthesis of new class of DNA cross-linking agents, polyhydroxy 1-vinyl-tetrahydroindolizine derivatives.
RESUMO
A mild and highly efficient one-pot method has been developed for the stereoselective synthesis of structurally diverse novel iminosugar C-aryl glycosides. The generality of this methodology is demonstrated with a wide variety of aryl nucleophiles and amines. The synthetic potential of this methodology is further shown in the domino synthesis of iminosugar based hybrid molecules.