Sharpless Catalytic Asymmetric Dihydroxylation Research Articles

An efficient synthesis of enantiomerically pure 2-[(2 R)-arylmorpholin-2-yl]ethanols, key intermediates of tachykinin receptor antagonist

We report herein an efficient and practical synthetic method for the preparation of enantiomerically pure 2-[(2 R)-arylmorpholin-2-yl]ethanols 1a– d, key intermediates of tachykinin receptor antagonist. Sharpless catalytic asymmetric dihydroxylation of 4a– d was employed to introduce the required absolute stereochemistry, and cyclization of 7a– d was accomplished by the Mitsunobu reaction.

ChemInform Abstract: Enantioselective Synthesis of Eucomols Using Sharpless Catalytic Asymmetric Dihydroxylation.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform Abstract: A Soluble Polymer‐Bound Approach to the Sharpless Catalytic Asymmetric Dihydroxylation (AD) Reaction: Preparation and Application of a ((DHQD) 2PHAL‐PEG‐OMe) Ligand.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

A soluble polymer-bound approach to the Sharpless catalytic asymmetric dihydroxylation (AD) reaction: Preparation and application of a [(DHQD) 2PHAL-PEG-OMe] ligand

The synthesis of a soluble polymer-bound (DHQD) 2PHAL ligand 1 and its successful application in the catalytic asymmetric dihydroxylation reaction are described. The results highlight that the soluble polymer-bound ligand approach offers all the benefits associated with insoluble supports but with the key advantages of increased reactivity and enantioselectivity inherent with solution-phase methodology.

Asymmetric Synthesis of 2-Acetyl-4(5)-(1,2,3,4-tetrahydroxybutyl)imidazoles

A method for preparing the eight stereoisomers of the biologically active compound (1R,2S,3R)-2-acetyl-4(5)-(1,2,3,4-tetrahydroxybutyl)imidazole (THI, 1) is reported. This method employs a palladium(0)-catalyzed coupling of 1-(ethoxymethyl)-4-iodoimidazole (7) to functionalized vinylstannanes (R)- or (S)-12a,b or 13a,b or 1-alkynylstannanes (R)- or (S)-6a,b to introduce the C-4 imidazole four-carbon side chain. The 1,2-dihydroxy functionality of the butyl side chain was introduced by Sharpless catalytic asymmetric dihydroxylation reactions.

Enantioselective Synthesis of Eucomols Using Sharpless Catalytic Asymmetric Dihydroxylation

Enantioselective Synthesis of Eucomols Using Sharpless Catalytic Asymmetric Dihydroxylation

Enantioselective Syntheses of Syributin 1 and Novel C-Glycosidic Elicitors Syringolides 1 and 2

Concise enantioselective syntheses of syributin 1 (3) and the novel nonproteinaceous C-glycosidic elicitors syringolides 1 and 2 (1 and 2, respectively), isolated from Pseudomonas syringae pv. tomato, are described. Syributin 1 was synthesized in one step by the Sharpless catalytic asymmetric dihydroxylation (AD reaction) of (1‘E)-3-(3‘-(octanoyloxy)-1‘-propenyl)but-2-en-4-olide (13) in 72% yield with >98% ee. Furthermore, alkylation of (1‘R,2‘R)-3-[1‘-(tert-butyldimethylsiloxy)-2‘,3‘-(isopropylidenedioxy)propyl]but-2-en-4-olide (20), prepared from (1‘E)-3-[3‘-(tert-butyldimethylsiloxy)-1‘-propenyl]but-2-en-4-olide (11) by the AD reaction, with hexanal or octanal by Jefford's procedure at the α position to the lactone carbonyl group gave adduct 21 or 22 in good yield. Oxidation of 21 or 22, followed by removal of the protecting groups, provided syringolide 1 or 2, respectively.

Synthesis of Tuckolide, a New Cholesterol Biosynthesis Inhibitor.

Tuckolide (decarestrictine D), a 10-membered lactone isolated from P. corylophilum and polyporus tuberaster fungi that potently inhibits cholesterol biosynthesis, was synthesized. The key steps include a Sharpless catalytic asymmetric dihydroxylation reaction (AD) of the methoxymethyl (MOM) ether protected diene 2 and a direct Corey-Nicolaou lactonization reaction of seco-acid 1with added silver perchlorate. The selectivity of the dihydroxylation step was found to be highly dependent on the nature of the protecting group adjacent to the diene in 2. The selectivity of the asymmetric dihydroxylation reaction of 2 indicates that both steric and electronic effects can lead to significant amounts of the undesired isomers. This synthesis establishes the absolute stereochemistry of tuckolide showing the C3 hydroxyl bearing carbon with an S-configuration comparable in an absolute sense to that in the lactone portion of the HMG-CoA reductase inhibitor compactin.

Asymmetric synthesis of (1R, 2S, 3R)-2-Acetyl-4(5)-(1,2,3,4-tetrahydroxybutyl)imidazole

A method for preparing the biologically active compound (1 R , 2 S , 3 R )-2-acetyl-4(5)-(1,2,3,4-tetrahydroxybutyl)imidazole 1 using a palladium (0) catalysed coupling of 1-ethoxymethyl-4-iodoimidazole 2 to the functionalised vinylstannane 3 and the Sharpless catalytic asymmetric dihydroxylation is reported. Graphic

Enantioselective synthesis of 20(S)-camptothecin using sharpless catalytic asymmetric dihydroxylation

The homochiral key intermediate 2 of 20(S)-camptothecin was prepared enantioselectively by using catalytic asymmetric dihydroxylation as the key reaction.

ChemInform Abstract: Anomalous Enantioselectivity in the Sharpless Catalytic Asymmetric Dihydroxylation Reaction of 1,1‐Disubstituted Allyl Alcohol Derivatives.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Anomalous enantioselectivity in the Sharpless catalytic asymmetric dihydroxylation reaction of 1,1-disubstituted allyl alcohol derivatives

The Sharpless asymmetric dihydroxylation (AD) reaction has been examined on a number of 1,1-disubstituted allyl alcohol derivatives. In the majority of substrates studied, the product diols had ee's in the 11–91% range and had absolute stereochemistry opposite to that predicted using the Sharpless steric model.

(+)- Exo-brevicomin via an organometallic boulevard

The brevicomin carbon skeleton was efficiently constructed through a novel 2 + 3 + 4 sequence via organocuprate and Suzuki couplings. The Sharpless catalytic asymmetric dihydroxylation provided either naturally (+)-exo-brevicomin (+)-7 or its enantiomer, (−)-7, both in 95% ee, in 61% overall yield from allyl bromide.