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1.
2.
An enantioselective and diastereocontrolled approach to 8a-epi-d-swainsonine has been developed from achiral furfural. The key step to this synthesis was a one-pot procedure for the hydrogenolytic removal of two protecting groups and two intramolecular reductive amination reactions. The absolute stereochemistry was introduced by asymmetric Noyori reduction of furfuryl ketone. This route relies on diastereoselective palladium-catalyzed glycosylation to install the anomeric bond, and Luche reduction, diastereoselective dihydroxylation to set up the manno-stereochemistry of the indolizidine precursor.  相似文献   

3.
A de novo asymmetric synthesis of (R)- and (S)-fridamycin E has been achieved. The entirely linear route required only nine steps from commercially available starting materials (16% overall yield). Key transformations included a Claisen rearrangement, a Sharpless dihydroxylation and a cobalt-catalyzed epoxide carbonylation to give a β-lactone intermediate. Antibacterial activities were determined for both enantiomers using two strains of E. coli, with the natural (R)-enantiomer showing significant inhibition against a Gram-(+)-like imp strain (MIC = 8 μM).  相似文献   

4.
Guo H  O'Doherty GA 《Organic letters》2006,8(8):1609-1612
[reaction: see text] The enantioselective syntheses of both enantiomers of the indolizidine natural product swainsonine have been achieved in 13 steps from furan. The indolizidine ring system is installed by a one-pot hydrogenolysis of both an azide and an O-Bn group along with an intramolecular reductive amination reaction. The asymmetry of swainsonine was introduced by Noyori reduction of an acylfuran. This route relies upon an Achmatowicz rearrangement, a diastereoselective palladium-catalyzed glycosylation, Luche reduction, and a dihydroxylation reaction.  相似文献   

5.
[reaction: see text] The enantioselective synthesis of anamarine has been achieved in 21 steps. The route relies on enantio- and regioselective Sharpless dihydroxylation of dienoate ester and zinc borohydride reduction to establish the C-8-C-11 stereochemistry. A diastereoselective Leighton allylation established the desired C-5 stereochemistry. The route has also been used to prepare two diastereoisomers of anamarine in 14 steps.  相似文献   

6.
[reaction: see text] A highly stereoselective synthesis of l-2-deoxy-beta-ribo-hexopyranosyl nucleosides from 6-chloropurine and Boc-protected pyranone has been developed. Our approach relies on the iterative application of a palladium-catalyzed N-glycosylation, diastereoselective reduction, and reductive 1,3-transposition. This strategy is amenable to prepare various natural and unnatural hexopyranosyl nucleosides analogues.  相似文献   

7.
Li M  O'Doherty GA 《Organic letters》2006,8(18):3987-3990
The enantioselective synthesis of the spiroketal/macrolide natural product milbemycin beta3 has been achieved in 22 steps and 2.8% overall yield from an achiral dienoate. The spiroketal ring system was installed by three sequential asymmetric hydrations followed by sprioketalization. Both the absolute and relative stereochemistry of milbemycin beta3 was introduced by two Sharpless asymmetric dihydroxylations, two pi-allylpalladium-catalyzed reductions, and an iridium-catalyzed hydrogen migration/Claisen rearrangement to install the C-12 stereocenter.  相似文献   

8.
For the last ten years our group has been working toward the development of an asymmetric hydration approach to polyketide natural products based on the regioselective hydration of di- and tri-enoates. Key to the success of this approach is the recognition that both high regiocontrol and asymmetric induction could be obtained by the use of a Sharpless asymmetric dihydroxylation reaction. Herein we describe the development of the method and its application to natural product total synthesis.  相似文献   

9.
An efficient enantioselective synthesis of (+)-isofregenedol was achieved in 13 steps from commercially available cyclohexene oxide without the use of protecting groups. The tetrahydronaphthalenic core of isofregenedol was obtained via a gold(I)-catalyzed benzannulation recently developed in our laboratory.  相似文献   

10.
An asymmetric ring-opening reaction of meso-aziridines with TMSN3 was developed using a catalyst prepared from Y(OiPr)3 and chiral ligand 2 in a 1:2 ratio. Excellent enantioselectivity was realized from a wide range of substrates with a practical catalyst loading. The products were efficiently converted to enantiomerically enriched 1,2-diamines, which are versatile chiral building blocks for pharmaceuticals and chiral ligands. This reaction was applied to a catalytic asymmetric synthesis of Tamiflu, a very important anti-influenza drug containing a chiral 1,2-diamino functionality.  相似文献   

11.
The enantioselective syntheses of several protected 4-substituted syn-3,5-dihydroxy carboxylic esters have been achieved from the corresponding achiral (E,E)- or (E,Z)-1,3-dienoates. The route relies upon an enantio- and regioselective Sharpless dihydroxylation and a palladium-catalyzed reduction to form gamma-substituted delta-hydroxy-1-enoates. The resulting delta-hydroxy-1-enoates are subsequently converted into benzylidene-protected 4-substituted syn-3,5-dihydroxy carboxylic esters in one step. The benzylidene-protected 3,5-dihydroxy carboxylic esters are produced in good overall yields (20-54%) and high enantiomeric excess (73-97% ee).  相似文献   

12.
An efficient and general method for the synthesis of 1,4-dihydropyridines and pyridines based on a lithiation/isomerization/intramolecular carbolithiation sequence is reported. This procedure provides an efficient, divergent, and straightforward entry to a wide range of polysubstituted dihydropyridines and pyridines starting from readily available N-allyl-ynamides.  相似文献   

13.
Teleocidin B analogs have been synthesized in 24 steps and 1.9% overall yield. The key steps include aromatic Claisen rearrangement, intramolecular Heck reaction of a tetra-substituted alkene, and ruthenium (II) catalyzed indole cyclization. Teleocidin and the new analogs promote cell spreading on fibroblast cells that were treated with amino-Nogo, an inhibitor of cell spreading.  相似文献   

14.
Oligosaccharide synthesis is hindered by the need for multiple steps as well as numerous selective protections and deprotections. Herein we report a highly efficient de novo route to various oligosaccharide motifs, of use for biological and medicinal structure activity studies. The key to the overall efficiency is the judicious use of asymmetric catalysis and synthetic design. These green principles include the bidirectional use of highly stereoselective catalysis (Pd(0)-catalyzed glycosylation/post-glycosylation). In addition, the chemoselective use of C-C and C-O π-bond functionality, as atom-less protecting groups as well as an anomeric directing group (via a Pd-π-allyl), highlights the atom-economical aspects of the route to a divergent set of natural and unnatural oligosaccharides (i.e., various d-/l-diastereomers of oligosaccharides as well as deoxysugars which lack C-2 anomeric directing groups). For example, in only 12 steps, the construction of a highly branched heptasaccharide with 35 stereocenters was accomplished from an achiral acylfuran.  相似文献   

15.
Li M  O'Doherty GA 《Organic letters》2006,8(26):6087-6090
[Structure: see text] A de novo approach to the formal total synthesis of the macrolide natural product (-)-apicularen A has been achieved in 18 steps from achiral starting materials. Both the absolute and relative stereochemistries of apicularen A were introduced by a Sharpless asymmetric dihydroxylation, a pi-allyl-palladium catalyzed reduction, a stereoselective reduction, and a base-promoted transannulation to install the C-9 stereocenter.  相似文献   

16.
Yu X  O'Doherty GA 《Organic letters》2008,10(20):4529-4532
A highly enantio- and diastereoselective synthesis of an alpha-L-aculose, alpha-L-rhodinose, and beta-D-olivose trisaccharide is described. The key transformations include the palladium-catalyzed glycosylation, Myers' reductive rearrangement, diastereoselective dihydroxylation, and regioselective Mitsunobu inversion. Significant apoptotic antitumor activity was found for this trisaccharide, which has implication for vineomycin B2 and PI-080 structure-activity relationship.  相似文献   

17.
A novel integrated bio- and chemocatalytic approach to the de novo catalytic asymmetric synthesis of saccharides has been developed. Acetoxypyranones obtained enantiopure by enzymatic resolution have been shown to undergo highly stereoselective palladium-catalyzed formal O-glycoside bond formation. The combination of these protocols can be applied to the iterative asymmetric catalytic synthesis of saccharides.  相似文献   

18.
A de novo approach to the formal total synthesis of the macrolide natural product (-)-virginiamycin M2 has been achieved via a convergent approach. The absolute and relative stereochemistry of the nonpeptide portion of (-)-virginiamycin M2 was introduced by two Sharpless asymmetric dihydroxylation reactions.  相似文献   

19.
A divergent, practical, and efficient de novo synthesis of fully functionalized L-colitose (3,6-dideoxy-L-galactose), 2-epi-colitose (3,6-dideoxy-L-talose), and L-rhodinose (2,3,6-trideoxy-L-galactose) building blocks has been achieved using inexpensive, commercially available (S)-ethyl lactate as the starting material. The routes center around a diastereoselective Cram-chelated allylation that provides a common homoallylic alcohol intermediate. Oxidation of this common intermediate finally resulted in the synthesis of the three monosaccharide building blocks.  相似文献   

20.
Butenolides 5a and 13 were used as optically active templates in the de novo synthesis of 4'-disubstituted nucleoside analogues. The butenolides were reduced and acylated in situ to give acetates 10 and 14. Vorbrüggen coupling gave the protected nucleoside analogues 11 and 15. Reduction of 11 gave 4'-ethoxy-2',3'-dideoxythymidine (6) and deprotection of 15 gave 4'-ethoxy-2',3'-dideoxydidehydrothymidine (7). The cis-dihydroxylation of a variety of butenolides occurred with the major product formed from oxidation of the beta-face.  相似文献   

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