Showing papers on "Total synthesis published in 1991"
143 citations
118 citations
TL;DR: In this article, the intramolecular coupling reaction of an organostannane with an electrophile was used to construct β-resorcyclic macrolides.
Abstract: The β-resorcyclic macrolides are a class of naturally occurring 12- and 14-membered macrolides. Zearalenone (1), a 14-membered macrolide of this type, displays useful biological activity, which has led to great synthetic interest. In this paper the intramolecular coupling reaction of an organostannane with an electrophile is used to construct β-resorcyclic macrolides. The intramolecular coupling of an aryl iodide with a vinylstannane provided the highest yield of lactones. This methodology was then used to prepare (S)-zearalenone (1)
114 citations
103 citations
TL;DR: The reaction cle de cette synthese totale est l'application de la reaction Becker-Alder au 5bromo-6methoxy-8-oxo-1-oxaspiro [25] octa-4,6-diene-4-carbaldehyde as discussed by the authors.
Abstract: La reaction cle de cette synthese totale est l'application de la reaction Becker-Alder au 5-bromo-6-methoxy-8-oxo-1-oxaspiro [25] octa-4,6-diene-4-carbaldehyde
96 citations
TL;DR: The first total synthesis of (−)-phyllanthose and (+)-phyllanthoside was reported in this paper, with the Koenigs-Knorr disaccharide construction and the Mitsunobu coupling of the aglycon and sugar.
Abstract: First total syntheses of (−)-phyllanthose and (+)-phyllanthoside. Key features of the scheme include the Koenigs-Knorr disaccharide construction and Mitsunobu coupling of the aglycon and sugar. Importantly, the Mitsunobu protocol comprises a simple, highly efficient new method for the stereoselective generation of β-glycosyl esters
91 citations
TL;DR: A convergent asymmetric synthesis of the polyether antibiotic ferensimycin B has been completed in this article, where vanadium-catalyzed internal epoxidation of a bis-homoallylic alcohol was employed to relay chirality from the C13 to the CI6 oxygen-bearing stereocenter.
Abstract: A convergent asymmetric synthesis of the polyether antibiotic ferensimycin B has been completed. Chiral enolate bond constructions were employed to establish seven of the 16 stereocenters of the subunits 35 and 52, which comprise the C& and CI&3 portions of ferensimycin B. The stereogenic centers at C3, C4, Cg, Clo, CI6, C,,, and CIS were incorporated through internal asymmetric induction, while those at Cm and C1l were established by using asymmetric epoxidation methodology. In this transformation, a vanadium-catalyzed internal epoxidation of a bis-homoallylic alcohol was employed to relay chirality from the C13 to the CI6 oxygen-bearing stereocenter. A final aldol addition reaction on intermediates devoid of protecting groups united the fragments 52 and 35 to provide synthetic ferensimycin B, whose absolute configuration was found to be
91 citations
TL;DR: In this paper, a highly convergent total synthesis of the anthelmintic macrolide avermectin B1a 1 is described, which includes selective ring opening of a symmetrical 1,4-bis-epoxide 4 followed by reaction with the anion derived from the 3-methyl-2-(1-methylpropyl)-6-phenylsulphonylpyran 3 to afford the ‘northern’ C(11)−C(25) fragment 39.
Abstract: A highly convergent total synthesis of the anthelmintic macrolide avermectin B1a 1 is described. The key features of this synthesis include the introduction of the C(11)–C(15) portion by selective ring opening of a symmetrical 1,4-bis-epoxide 4 followed by reaction with the anion derived from the 3-methyl-2-(1-methylpropyl)-6-phenylsulphonylpyran 3 to afford the ‘northern’ C(11)–C(25) fragment 39. Coupling of the derived C(11)–C(25) aldehyde unit 42 with a C(1)–C(10)‘southern’ fragment 2 was achieved via a novel deconjugative vinyl sulphone anion sequence. Macrolactonisation and subsequent introduction of the 3,4-double bond gave the aglycone portion 51. The oleandrosyloleandrose disaccharide was introduced by a novel silver-mediated coupling between the 5-acetylated aglycone 70 and the thiocarbonylimidazolide 69. Final deacetylation was accomplished using Super-Hydride to give the natural product 1.
89 citations
87 citations
85 citations
TL;DR: A review on N-acetylneuraminic acid is presented in this article in two parts, the first section details the literature on the total synthesis of Neu5Ac and the second part deals with the progress on the chemical and enzymatic glycosidation of sialic acid.
Abstract: A review on N-acetylneuraminic acid is presented in two parts. The first section details the literature on the total synthesis of Neu5Ac. The second part deals with the progress on the chemical and enzymatic glycosidation of sialic acid
TL;DR: In this paper, the dibenzyl acetal of (-)-(1S,4S)-7-oxabicyclo[2.2.1]hept-5-en-2-one ((-)-5) led to (+)-( 1S,5S,6S,7S,8R,8aS)-8-(benzyloxy)-6,7-epoxy-1-hydroxyoctahydroindolizidin -5-one) followed by reduction of the lactam and dep
Abstract: Bromination of the dibenzyl acetal of (-)-(1S,4S)-7-oxabicyclo[2.2.1]hept-5-en-2-one ((-)-5) led to (+)-(1S,5S,6S,7S)-6-endo-(benzyloxy)-5-exo-bromo-7-oxabicyclo[2.2.1]hept an-2-one (25). Baeyer-Villiger oxidation of 25 gave 2-O-benzyl-3-bromo-3,5-dideoxy-beta-L-arabino-hexofuranosidurono-6,1-lac tone (26). Methanolysis of 26 afforded the corresponding methyl (methyl alpha-beta-L-arabinofuranosid)uronates (27 + 28). The alpha anomer 27 was reduced with DIBAH into methyl 2-O-benzyl-3-bromo-3,5-dideoxy-beta-L-arabino-hexofuranoside (29). Mesylation of the primary alcohol, followed by treatment with NH3 gave methyl 2-O-benzyl-3,5-6-trideoxy-3,6-imino-beta-L-lyxo-hexofuranoside (32). Acetylation of the amine with ClCH2COCl, acetolysis of the methyl furanoside followed by Arbuzov condensation with (EtO)3P, and then intramolecular Horner-Emmons reaction led to (5S,6S,7S)-7-hydroxy-5-(benzyloxy)-1-azabicyclo[4.3.0]non-3-en-2-one (37). Base-catalyzed hydrolysis of the corresponding epoxide 43 ((1S,6S,7S,8R,8aS)-8-(benzyloxy)-6,7-epoxy-1-hydroxyoctahydroindolizidin -5-one) followed by reduction of the lactam and deprotection of the alcoholic functions afforded (+)-castanospermine ((+)-1). The conversion of (-)-5 into (+)-1 was highly stereoselective, requiring the isolation of 10 synthetic intermediates and with an overall yield of 15.2%. Reduction of 43 with BH3.Me2S or its treatment with HF.Et3N allowed one to prepare readily (+)-6-deoxycastanospermine ((+)-2 and 6-deoxy-6-fluorocastanospermine ((+)-3). The crystal structure of (+)-3 is also reported.
TL;DR: The first total synthesis of AI-77-B (1) was achieved in a stereoselective and convergent manner as mentioned in this paper, where the dihydroisocoumarin part 2 was constructed in one step through 1,2-addition of the benzylic anion 17b to Boc-L-leucinal 7b.
TL;DR: The first total synthesis of the antibiotic (−)-hygromycin A (1) has been achieved by a coupling reaction of the sugar moiety and the cyclitol moiety.
Abstract: The first total synthesis of the antibiotic (−)-hygromycin A (1) has been achieved by a coupling reaction of the sugar moiety (2) and the cyclitol moiety (3). Both components were synthesized in homochiral forms starting from D-glucose. This synthesis fully confirmed the unique structure of 1, which is much different from other usual aminocyclitol antibiotics
TL;DR: In this article, a five-step total synthesis of cis-and trans-trikentrin A is detailed and is based on the implementation of two sequential heteroaromatic azadiene Diels-Alder reactions constituting a general approach to the preparation of substituted indoles.
Abstract: A five-step total synthesis of cis- and trans-trikentrin A is detailed and is based on the implementation of two sequential heteroaromatic azadiene Diels-Alder reactions constituting a general approach to the preparation of substituted indoles
TL;DR: In this paper, the stereoselective total synthesis of the title compound starting from D-glucose is described, and the key steps in this synthesis are Ferrier rearrangement to construct the optically active cyclohexenone (C-ring), and Pd-catalyzed intramolecular Heck reaction to build the phenanthridone skeleton.
TL;DR: In this article, a total synthesis of (+/-)-alpha-and (+/--gamma-lycorane is described, where the key steps in the syntheses are the stereocontrolled palladium-catalyzed intramolecular 1,4-chloroamidation of 12 to 13 and the subsequent anti-stereoselective copper-calyzed S(N)2' reaction of allylic chloride 13 with [3,4-(methylenedioxy)phenyl]magnesium bromide to give 14.
Abstract: Total syntheses of (+/-)-alpha-and (+/-)-gamma-lycorane are described. The key steps in the syntheses are the stereocontrolled palladium-catalyzed intramolecular 1,4-chloroamidation of 12 to 13 and the subsequent anti-stereoselective copper-catalyzed S(N)2' reaction of allylic chloride 13 with [3,4-(methylenedioxy)phenyl]magnesium bromide to give 14. Hexahydroindole 14 has the required relative stereochemistry between carbons 3a, 7, and 7a for alpha-lycorane (1a) and was transformed to the latter via 15 and 16. The epimeric gamma-lycorane (2) was obtained by performing the Bischler-Napieralski cyclization on 14, which led to a highly stereoselective isomerization to give exclusively 17. Compound 17 was subsequently transformed to 2. The overall yield from ester 8 to (+/-)-alpha- and (+/-)-gamma-lycorane was 40 and 36%, respectively.
TL;DR: A total synthesis of (+)-hydantocidin 1, a new class of ribofuranose derivative exhibiting herbicidal activity, was reported in this paper, where the spiro-hydantoin ring at the anomeric position of D -ribofuranoses was constructed from substituted hydantoin derivatives 6, 7, and 12 through acid and base-promoted cyclization methods.
TL;DR: In this article, a general strategy for the synthesis of C 15 halogenated tetrahydrofuranoid lipids from red algae of the genus Laurencia has been developed.
Abstract: A general strategy for the synthesis of C 15 halogenated tetrahydrofuranoid lipids from red algae of the genus Laurencia has been developed. The central step is the convenient formation of hydrobenzofuranone (±)-5 on a large scale, and with complete stereocontrol, from the acid-catalyzed condensation of 1-vinylcyclopentanediol (3) and α-(benzyloxy) acetaldehyde (Scheme II). Starting with the chiral, nonracemic (1S,2R)-diol 3, hydrobenzofuranone (-)-5 is also available in good enantiomeric purity (Scheme V). The total synthesis of (±)-trans-kumausyne from rac-5 is accomplished in 13 steps and >5% overall yield
TL;DR: In this article, a convergent total synthesis of (−)-erythronolide B (5) and two 9-dihydro derivatives (52 and 54) from (R)-2,3-O-isopropylideneglyceraldehyde (20) as the only source of chirality is described.
Abstract: A convergent total synthesis (22 steps on the longest linear route) of (−)-erythronolide B (5) and two 9-dihydro derivatives (52 and 54) thereof from (R)-2,3-O-isopropylideneglyceraldehyde (20) as the only source of chirality is described. A key step of the synthesis is the regio- and stereocontrolled coupling of the allyl sulfide anion 39 and ketone 26 which can be directed to either α-adduct 40 or 41 by an appropriate choice of the conditions (Scheme V, table II). From 40 and 41 the seco acids 47 and 49 are prepared, which are smoothyly macrolactonized to 50 and 51 according to a modified Yamaguchi procedure. Hydroboration of 50 and 51 proceeds under macrocyclic stereocontrol to afford the 9-dihydroerythronolide B derivatives 52 and 54, of which 54 is converted in 5 by a known oxidation-deketalization sequence
TL;DR: In this article, a conceptually new approach to Strychnos alkaloids was reported, characterized by the concise evolution of the strychnan skeleton by ''aza-Cope-Mannich» rearrangement of a 2-azabicyclo[3.2.1] octane precursor.
Abstract: We report a conceptually new approach to Strychnos alkaloids, which is characterized by the concise evolution of the strychnan skeleton by «aza-Cope-Mannich» rearrangement of a 2-azabicyclo[3.2.1]octane precursor