Stereoselective Synthesis of the LM Ring Moiety of Ciguatoxin: Reagent Control of Asymmetric Dihydroxylation

1997 ◽  
Vol 26 (9) ◽  
pp. 845-846 ◽  
Author(s):  
Tohru Oishi ◽  
Mitsuru Shoji ◽  
Naomi Kumahara ◽  
Masahiro Hirama
Keyword(s):  
Stereoselective Synthesis ◽  
Asymmetric Dihydroxylation

Asymmetric dihydroxylation of stachysterone C: stereoselective synthesis of 24-epi-abutasterone

Tetrahedron ◽  
1998 ◽  
Vol 54 (12) ◽  
pp. 2795-2800 ◽  
Author(s):  
Boon-ek Yingyongnarongkul ◽  
Apichart Suksamrarn
Keyword(s):  
Stereoselective Synthesis ◽  
Asymmetric Dihydroxylation

Stereoselective synthesis of multiply substituted [1,2]oxazinan-3-ones via ring-closing metathesis

2005 ◽  
Vol 83 (2) ◽  
pp. 93-103 ◽  
Author(s):  
Gennady V Shustov ◽  
Melanie K Chandler ◽  
Saul Wolfe
Keyword(s):  
Stereoselective Synthesis ◽  
High Yield ◽  
Acryloyl Chloride ◽  
Successive Reaction ◽  
Ring Closing Metathesis ◽  
Silver Triflate ◽  
Asymmetric Dihydroxylation ◽  
Single Diastereomer ◽  
Cyclic Sulfite ◽  
Hydroxy Esters

The title compounds are α-amino acids whose nitrogen atoms are enclosed within 4,5-disubstituted, six-membered cyclic hydroxamates and they are of interest as potential β-lactam surrogates. The compounds have been synthesized in the present work by functionalization of the double bonds of N-substituted 6H-[1,2]oxazin-3-ones, which are obtained upon successive reaction of the triflates of S-α-hydroxy esters with O-allylhydroxylamine and acryloyl chloride, followed by cyclization of the resulting R-α-N-acryloyl-N-allyloxyamino esters in the presence of the ring-closing metathesis (RCM) catalyst bis(tricyclohexylphosphine)benzylideneruthenium dichloride. The olefins are also accessible, but less efficiently so, by a Wittig sequence that employs bromoacetyl bromide in place of acryloyl chloride, followed successively by triphenylphosphine, silver triflate, ozonolysis, and cyclization. Asymmetric dihydroxylation of these chiral olefins affords a single diastereomer in high yield having either the αR,4S,5S- or the αR,4R,5R configuration, depending on the auxiliary. The configuration of the αR,4R,5R isomer has been confirmed by its conversion to (αR,4S,5R)-2-(α-carboxyethyl)-4-phenylacetylamino-5-hydroxy-1,2-oxazinan-3-one, whose αR,4R,5S diastereomer was previously prepared from L-ascorbic acid. With N-bromosuccinimide in aqueous dimethylformamide, a 6H-[1,2]oxazin-3-one afforded a separable 1:1 mixture of bromohydrins, which could be cyclized to epoxides or hydrogenolyzed to 5-hydroxy-1,2-oxazinan-3-ones. Key words: penicillin surrogates, asymmetric dihydroxylation, bis(tricyclohexylphosphine)benzylideneruthenium dichloride, cyclic sulfite, epoxides, azidohydrin, bromohydrin.

Total Synthesis of Camptothecins: An Update

Synlett ◽  
2017 ◽  
Vol 28 (10) ◽  
pp. 1134-1150 ◽  
Author(s):  
Fen-Er Chen ◽  
Lei Chen
Keyword(s):  
Total Synthesis ◽  
Stereoselective Synthesis ◽  
Enantioselective Synthesis ◽  
The Novel ◽  
Asymmetric Dihydroxylation ◽  
New Methods ◽  
Considerable Research ◽  
Catalytic Asymmetric ◽  
Synthetic Approaches ◽  
Asymmetric Hydroxylation

Over the last few decades, considerable research efforts have been directed toward the development of effective chemical syntheses of camptothecin and its analogs. The last comprehensive review of this area was published in 2003 and many effective new methods have since been reported for the stereoselective synthesis of the camptothecin alkaloids. In this account, we have summarized most of the novel synthetic approaches developed for the synthesis of camptothecins during the last decade. We have focused on strategies for the construction of the pentacyclic ring system and the different methods used to install the chiral quaternary center on the E ring of camptothecin.1 Introduction2 Synthesis of Racemic Camptothecins3 Enantioselective Synthesis of Camptothecins3.1 Sharpless Asymmetric Dihydroxylation3.2 Catalytic Asymmetric Cyanosilylation3.3 Auxiliary-Induced Asymmetric Carbonyl Addition3.4 Catalytic Asymmetric Ethylation3.5 Asymmetric Hydroxylation4 Conclusion

Stereoselective Synthesis of 1′,2′-cis-Disubstituted Carbocyclic ribo-Nucleoside Analogues

Synthesis ◽  
2017 ◽  
Vol 50 (06) ◽  
pp. 1264-1274 ◽  
Author(s):  
Chris Meier ◽  
Simon Weising ◽  
Ilaria Torquati
Keyword(s):  
Building Block ◽  
Stereoselective Synthesis ◽  
Nucleoside Analogues ◽  
Convergent Synthesis ◽  
Enantiomerically Pure ◽  
Efficient Strategy ◽  
Asymmetric Dihydroxylation

Herein we disclose an efficient strategy for the convergent synthesis of 1′,2′-cis-disubstituted carbocyclic ribo-nucleoside analogues. Starting from an enantiomerically pure cyclopentenol precursor, the key step for the preparation of the highly functionalized carbocyclic building block is an asymmetric dihydroxylation. Employing different variants of the Mitsunobu protocol, the condensation with all-natural nucleobases or their precursors affords a series of ribo-configured carbocyclic 1′,2′-cis-disubstituted nucleoside analogues.

scholarly journals Stereoselective Synthesis of Flavonoids. Part 8. Free Phenolic Flavan-3-ol Diastereoisomers

1999 ◽  
Vol 23 (10) ◽  
pp. 606-607
Author(s):  
J. J. Nel Reinier ◽  
Hendrik van Rensburg ◽  
Pieter S. van Heerden ◽  
Daneel Ferreira
Keyword(s):  
Stereoselective Synthesis ◽  
Enantiomeric Excess ◽  
Asymmetric Dihydroxylation ◽  
Acid Catalyzed ◽  
Subsequent Acid

Asymmetric dihydroxylation of a series of poly- O-methoxymethyl-1,3-diarylpropenes with AD-mix-α or AD-mix-β and subsequent acid-catalyzed cyclization of the intermediate syn-diols permits the first synthetic access to all four diastereoisomers of free phenolic flavan-3-ols in high enantiomeric excess and yield.

scholarly journals Stereoselective synthesis of the C79–C97 fragment of symbiodinolide

2013 ◽  
Vol 9 ◽  
pp. 1931-1935 ◽  
Author(s):  
Hiroyoshi Takamura ◽  
Takayuki Fujiwara ◽  
Isao Kadota ◽  
Daisuke Uemura
Keyword(s):  
Molecular Weight ◽  
Natural Product ◽  
Stereoselective Synthesis ◽  
Marine Natural Product ◽  
Synthetic Route ◽  
Asymmetric Dihydroxylation

Symbiodinolide is a polyol marine natural product with a molecular weight of 2860. Herein, a streamlined synthesis of the C79–C97 fragment of symbiodinolide is described. In the synthetic route, a spiroacetalization, a Julia–Kocienski olefination, and a Sharpless asymmetric dihydroxylation were utilized as the key transformations.

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