Showing papers on "Total synthesis published in 1992"
347 citations
TL;DR: A convergent asymmetric synthesis of the marine natural product calyculin A has been accomplished through the union of the two subunits comprising the C 1 -C 25 and C 26 -C 37 portions of the molecule as discussed by the authors.
Abstract: A convergent asymmetric synthesis of the marine natural product calyculin A has been accomplished through the union of the two subunits comprising the C 1 -C 25 and C 26 -C 37 portions of the molecule. These fragments were constructed utilizing auxiliary-based asymmetric aldol, alkylation, hydroxylation, and Michael reactions to establish 10 of the 15 stereogenic centers. The remaining chirality was incorporated through internal asymmetric induction.Stereoselective Wittig coupling of the two fragment and subsequent deprotection provided synthetic calyculin A
247 citations
TL;DR: In this article, the first total synthesis of discorhabdin C, which was isolated from the sponge of Latrunculia du Bocagein New Zealand, was achieved.
Abstract: Hypervalent iodine oxidation of O-silylated phenols bearing various types of aminoquinones at the para position in 2,2,2-trifluoroethanol gave azacarbocyclic spiro dienones in good yields. Using this method, the first total synthesis of discorhabdin C, which was isolated from the sponge of Latrunculia du Bocagein New Zealand, was achieved
156 citations
154 citations
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144 citations
TL;DR: In this paper, the undecose moiety of hikizimycin was constructed efficiently by employing the strategy of two-directional chain synthesis, including advantages and challenges.
Abstract: Hikizimycin (anthelmycin) is a nucleoside antibiotic and anthelmintic agent that represents the most structurally complex member of the long-chain carbohydrate class of natural products. The undecose moiety of hikizimycin was constructed efficiently by employing the strategy of two-directional chain synthesis. A description of this approach, including the advantages and challenges, is provided. In addition, the methods that were utilized to solve the remaining problems associated with the synthesis of hikizimycin are reported. The synthesis confirms the assigned structure of the natural product
129 citations
TL;DR: The use of t-butyl-3-oxobutanthioate and t -butyl 4-diethylphosphono-3oxobuttanthioates for the preparation of homologated derivatives suitable for amination in the presence of trifluoroacetate to afford the corresponding β-ketoamides is discussed in this paper.
118 citations
TL;DR: In this article, a six-step route involving selective dealkylation of bikaverin-dimethylether 6 was used for the synthesis of BIKAVERIN.
114 citations
TL;DR: In this paper, the total synthesis of two novel polymerizable phosphatidylcholines has been accomplished using 3-(4-methoxybenzyl)-sn-glycerol 10 as starting material.
Abstract: The total synthesis of two novel polymerizable phosphatidylcholines has been accomplished using 3-(4-methoxybenzyl)-sn-glycerol 10 as starting material. Diacylation of 10 with 13-tetradecynoic acid followed by oxidative coupling of the alkynes gives a 32-membered glycerol macrocycle . Sequential acylation of 10 with palmitic acid and 15-hexadecynoic acid followed by oxidative coupling gives bolaform , tethered at the 2-position of the glycerol. A new method for the cle avage of 4-methoxybenzyl ethers using dimethylboron bromide at -78 o C in dichloromethane is described
TL;DR: The first total synthesis of 14-membered para ansa cyclopeptide alkaloid F was reported in this article, where the pivotal transformations of the synthetic strategy are (1) a stereocontrolled approach for introducing the absolute stereochemistry at the α- and β-carbons of the parent β-hydroxyproline utilizing D-serine as a source of chirality; (2) cyclization to a rigid 14-mbered ring; and (3) introduction of the enamide double bond.
Abstract: The first total synthesis of the 14-membered para ansa cyclopeptide alkaloid (-)-nummularine F is reported. The pivotal transformations of the synthetic strategy are (1) a stereocontrolled approach for introducing the absolute stereochemistry at the α- and β-carbons of the parent β-hydroxyproline utilizing D-serine as a source of chirality; (2) cyclization to a rigid 14-membered ring; and (3) introduction of the enamide double bond. The synthesis began with the conversion of D-serine to (2S,3S)-3-(4-cyanophenoxy)-1-[(1,1-dimethylethoxy)carbonyl]proline.After conversion of the cyano function to a formyl group, a Henry reaction between the 4-formylphenoxy group and the anion of nitromethane gave a mixture of epimeric benzyl alcohols containing a terminal nitro group.The nitro group was reduced to an amine and coupled to Z-protected L-isoleucine to afford the desired acyclic precursor.Cyclisation was achieved by the coupling of the proline pentafluorophenyl ester and the amino group of the L-isoleucine.The enamide bond was introduced after cyclisation,via thermal selenoxide elimination
TL;DR: The total synthesis of the spiroketal ionophore antibiotic routiennocin 1 (CP-61,405) employing π-allyltricarbonyl iron lactone complexes is described in this paper.
TL;DR: In this article, the total synthesis of naturally occuring (-)-physostigmine is described, and the key element for the asymmetric induction is the chirality transfer from optically active 2-(alkylsulfinyl)indoles to indoline butyrolactones bearing two chiral centers.
Abstract: The total synthesis of naturally occuring (-)-physostigmine is described. The key element for the asymmetric induction is the chirality transfer from optically active 2-(alkylsulfinyl)indoles to indoline butyrolactones bearing two chiral centers. Novel features of this synthesis involve the use of a new class of sulfoxylating agents, N-(alkylsulfinyl)oxazolidinones, to prepare the starting indolyl sulfoxides and the correlation of the size of the alkyl group on the sulfoxide with the degree of asymmetric induction
TL;DR: The first total synthesis of (+)-laurencin (1) via intermediates 2−18 was described in this article, where a facile oxidative preparation of 2, an effective conversion of 9a to 11, and a SmI2-catalyzed elongation reaction of 15, providing 16a.
TL;DR: A general protocol for the enantiogenic total syntheses of a series of the 5-substituted 8-methylindolizidine class of alkaloids from the arrow poison frog is described in this paper.
Abstract: A general protocol for the enantiogenic total syntheses of a series of the 5-substituted 8-methylindolizidine class of alkaloids from the arrow poison frog, i.e., (-)-indolizidines 205A (1), 207A (2), 209B (3), and 235B (4), is described, in which a key step is the asymmetric intramolecular Diels-Alder reaction of the chiral N-acylnitroso compound 8 leading to the bicyclic oxazinolactam 7 which was utilized as a versatile common chiral intermediate for the preparation of these alkaloids
TL;DR: The overall strategy for the synthesis of vinblastine (1) is based upon the nonoxidative cleavage of the tertiary amine (+)-18 to generate the intermediate delocalized cation 18a, which in the presence of an electron-rich aromatic nucleophile can be trapped at C-18 to give the bisalkaloid analogues 19, 20, and 21.
Abstract: The overall strategy for the synthesis of vinblastine (1) is based upon the nonoxidative cleavage of the tertiary amine (+)-18 to generate the intermediate delocalized cation 18a, which in the presence of an electron-rich aromatic nucleophile can be trapped at C-18'to give the bisalkaloid analogues 19, 20, and 21. To ascertain the effect on C-18'stereochemistry with respect to C-2'and C4'stereochemistry, we have made a number of stereoisomers of the tetraacyclic amine 30
TL;DR: In this paper, the development of a unified synthetic strategy for the indole diterpene tremorgens has led to the first total synthesis of (+)-paspalicine and (+-paspalinine from 4a-methyl octahydro naphthalene-2,5 -dione.
Abstract: The development of a unified synthetic strategy for the indole diterpene tremorgens has led to the first total synthesis of (+)-paspalicine and (+)-paspalinine from 4a-methyl octahydro naphthalene-2,5 -dione
TL;DR: In this article, a tandem Katsuli-Sharpless asymmetric epoxidation and enantiospecific ring expansion of 2-alkyl(or 2-aryl)-2-cyclopropylideneethanols (1a-i) afforded chiral 1-alky(or 1-aryl)1-(hydroxymethyl)cyclobutanones (3a)-i) in high yields and high enantiomeric excess.
Abstract: A tandem Katsuli-Sharpless asymmetric epoxidation and enantiospecific ring expansion of 2-alkyl(or 2-aryl)-2-cyclopropylideneethanols (1a-i) afforded chiral 1-alkyl(or 1-aryl)-1-(hydroxymethyl)cyclobutanones (3a-i) in high yields and high enantiomeric excess. These compounds are potentially valuable synthons for the enantioselective creation of the quaternary carbons. Hence, this enabled us to accomplish a concise and enantioselective total synthesis of both (+)- and (-)-α-cuparenones
TL;DR: Cyclisation of 15via the derived aryl radical leads to spiropyrrolidinyl-oxindole 16, which is converted in three steps into the oxindole alkaloid horsfiline 3.
Abstract: Cyclisation of 15via the derived aryl radical leads to spiropyrrolidinyl-oxindole 16, which is converted in three steps into the oxindole alkaloid horsfiline 3.
TL;DR: Asymmetric synthesis of chiral (3R,4R)-3-[(1R)-1-[(tert-butyldimenthylsilyl)oxy]ethyl]-4-acetoxyazetidin-2-one (3) was achieved by utilizing a highly diastereoselective aldol-type reaction of acetaldehyde and the chiral tin(II) enolate of 5 as discussed by the authors.
Abstract: Asymmetric synthesis of 11, the precusor to chiral (3R,4R)-3-[(1R)-1-[(tert-butyldimenthylsilyl)oxy]ethyl]-4-acetoxyazetidin-2-one (3) was achieved by utilizing a highly diastereoselective aldol-type reaction of acetaldehyde and the chiral tin(II) enolate of 5. Similar diastereoselective alkylations of chiral and achiral tin(II) enolates 13a-d with chiral 3 were also performed to obtain the desired alkylated azetidin-2-ones (17a-d)