Letters in Organic Chemistry - Volume 2, Issue 4, 2005

Click chemistry, designated by Sharpless and his coworkers, is a modular approach that uses only the most practical and reliable chemical transformations. The Huisgen reaction, especially the newly developed copper(I)-catalyzed 1,2,3-triazole formation reaction between azides and alkynes, is regarded as the “cream of the crop” of click chemistry. In this review, we introduce the recent development of this reaction, Read More

The enantioselectivity of the titanium (IV)-BINOL catalyzed asymmetric Mannich-type reactions of nitrones can be enhanced by using additional chiral ligands. The best results are obtained with diols derived from D-mannitol.

In this communication a convenient and novel method for the synthesis of chiral N-substituted- (arabinopyrano)[3,4-b]morpholines of pharmacological interest from anhydro sugars is described.

A variety of allyl and benzyl alcohols are converted into their corresponding iodides using cesium iodide (CsI) in the presence of aluminum chloride (AlCl3) in acetonitrile under mild conditions.

A new synthetic approach directed toward the preparation of C1-C6 fragment of erythronolides is disclosed. The core of the process takes advantage of a highly stereoselective sequence based on a boron- mediated aldol reaction of a lactate-derived chiral ketone followed by a syn-reduction of the resulting adduct.

We present in this note the preparation of 1,5,6-trideoxy-1,5-imino-D-gluco-heptitol commonly known as 1-deoxy-homonojirimycin by a diastereoselective way. The polyhydroxylated piperidine has been obtained from a β-ketoester bearing a xylofuranose moiety.

24(S)- or 24(R)-Hydroxyl cholesterol was prepared in high stereoselectivity (up to 99% de), utilizing asymmetric alkynylation of isobutyraldehyde with steroidal alkyne catalyzed by Zn(OTf)2 respectively in the presence of (1S, 2S)-3-(t-butyldimethylsilyloxyl)-2-N, N-dimethylamino-1-(p-nitrophenyl)- propane-1-ol or its (1R, 2R)-enantiomer.

As a reagent for fabrication of carbohydrate-based functional materials, we prepared a photo-reactive fluorescent glycosyl reagent carrying α-mannoside and 4-azidophenyl group in our previous fluorescent β- peptide skeleton. The reagent increased fluorescence upon UV-irradiation in methanol, demonstrating its high potential utility.

A simple and effective method for the thionation of amides to thioamides using Al2O3-supported P4S10 was developed and applied to a series of amides including some heterocyclic examples. The reaction was best performed in anhydrous dioxane at reflux temperature. Yields ranging from 62 - 93% are comparable to, or superior to those obtained with Lawesson's reagent. The method uses inexpensive reagents and has the Read More

Neat imine 1a with alkylcyanoacetate 2 leads to new cyclohexenes by Michael-Michael initiated ring closure reaction at RT or under classical heating. Surprisingly, this cyclohexene is not formed under microwave. This is the first example of a reaction working under classical activation and not under microwaves. A mechanism and an explanation are proposed.

The synthesis of new dihydrothieno[2,3-g and 3,2-g](iso)quinoline-4,9-dione derivatives, as potential templates in development of new cytotoxic agents, was realized using microwave irradiation methodology.

1-Methanesulfonyloxy-2-methoxyethane (1; MsO-MOE) was used for alkylation of adenosine and 2-aminoadenosine. 2'-O-MOE derivatives of adenosine (3), 2-aminoadenosine (7) and guanosine (10) have been prepared in 47, 44 and 81% isolated yields, respectively. The stereochemistry of the pentofuranose rings of the isomeric 2'-O-MOE and 3'-O-MOE purine nucleosides is very similar and, moreover, alkylation of either Read More

A spermine functionalized perylene bisimide dye has been synthesized which is highly water soluble at neutral pH and binds effectively to DNA through electrostatic interactions as confirmed by fluorescence and AFM studies.

The modification on natural phosphate (NP) with sodium nitrate by calcination catalyzed Michael addition of mercaptans and amines to chalcone derivatives with high yields under mild reaction conditions. By-products of usual undesirable reaction in Michael condensation such as 1,2-addition, bis-addition and polymerization are not observed. The work-up procedure is simplified by simple filtration with the use of Na/NP-2. This c Read More

Anhydrous FeCl3 and FeCl3-SiO2 serve as Lewis acids for direct conversion of alcohols into pmethoxybezyl ethers using PMB-OH in good yields, the latter reagent was found to be effective in not only converting primary, allylic and propargylic alcohols selectively but also the pre-existing acid sensitive groups remained unscathed.

The polyene cyclization promoted by the cross conjugated α-carbomethoxy enone system has been successfully applied to facilitate the construction of the hydridane and hydroazulene framework containing a high level of functionalization.

We report here the synthesis of a new cyclopenta[b]naphthalene-4,7-dione via the first example of intramolecular electron transfer reaction from naphthoquinonic alkylating agent bearing a nitroalkane group at the position 3.

A novel linker for the solid-phase anchoring of heterocycles and phenol compounds is described.

Acylation of ortho-lithiated species derived from N,O-dipivaloyl-6-amino-5,8-dimethoxy-4-methyl- 2(1H)-quinolinone, followed by condensation with carbonyl reagents and in situ N-deprotection gave 7-alkyl or 6,7-dialkyl-9,10-dimethoxy-4-methyl-1,5-diaza-2(1H)-anthracenones, which were finally oxidised to the title compounds.