A facile access to 2-deoxy-l-ribose

The title compound was prepared in five steps starting from R-(+)-5-benzyloxymethyl-5H-furan-2-one 1 via syn-dihydroxylation of its double bond, regioselective tosylation of the 2-OH group in the thus obtained diol 2 followed by selective deoxygenation of that position.     

A novel and concise synthetic access to chiral 2-substituted-4-piperidone

A novel and concise synthetic access to enantiopure chiral 2-aryl/alkyl substituted 4-piperidone has been demonstrated.This new route features two key steps:the highly diastereoselective conjugate addition of homochiral lithium amides to trans-β-substituted-α,β-unsaturated methyl esters guaranteed the enantiopurity at 2 position(de19:1)and the intramolecular attacking of carbanions to methyl esters led to the formation of the piperidone ring.A wide range of substrates,including chiral2-aryl and 2-alkyl-4-piperidones,were successfully synthesized with modest to high yield.Moreover,some non-chiral3-substituted-4-piperidones were also synthesized with enhanced ring-formation yield,implicating the versatility of this method in construction of various piperidine rings.     

A facile access to indigodianiles

Bis‐imidoylchlorides derived from oxalic acid can easily be transformed into the corresponding bis‐imino benzotriazoles. The fact that benzotriazole is a well‐established leaving group has been exploited for an improved synthesis of indigodianiles. Employing metallic lithium, the benzotriazoles can be converted in a cascade reaction into indigo bis‐arylimines in yields up to 45%. Formation of the reduced form of dimeric isocyanides is suggested as a key step.     

A facile approach to the synthesis of chiral 2-substituted benzofurans

An effective route to chiral optically active 2-substituted benzofurans directly from carboxylic acids is reported. This procedure, which allows the preparation of alpha-alkyl-2-benzofuranmethanamines from N-protected alpha-amino acids without sensible racemization phenomena, proceeds in good yields under mild conditions with the help of microwave irradiation.     

Enantioselective Pd-catalyzed hydrogenation of fluorinated imines: facile access to chiral fluorinated amines

An enantioselective hydrogenation of simple fluorinated imines has been developed using Pd(OCOCF(3))(2)/(R)-Cl-MeO-BIPHEP as a catalyst, and up to 94% ee was achieved. This method provides an efficient route to enantioenriched fluorinated amines.     

A facile access to bridged 1,2,4-trioxanes

Bicyclo[3.2.1] type 1,2,4-trioxanes are readily synthesized from precursors that may form intramolecular hemiketals using UHP (H₂O₂-urea complex) as the source of the peroxy bond and p-TsOH or CSA as the catalyst. The ring closure through an intramolecular Michael addition occurred in a highly stereoselective way, giving only one diasteromer as shown by the NMR spectra.     

One-pot synthesis of 2-isopropyl-3-benzyl-1,3-thiazolidin-4-ones and 2-phenyl-3-isobutyl-1,3-thiazolidin-4-ones from valine, arenealdehydes and mercaptoacetic acid

A three-component one-pot synthesis of 2-isopropyl-3-benzyl-1,3-thiazolidin-4-ones and 2-phenyl-3-isobutyl-1,3-thiazolidin-4-ones from valine, arenealdehydes and mercaptoacetic acid with good yields is reported. Characterization of products was generally achieved by NMR techniques and specifically for 2-isopropyl-3-(4-nitrobenzyl)-1,3-thiazolidin-4-one by X-ray crystallography.     

Direct asymmetric Mannich reaction of phthalides: facile access to chiral substituted isoquinolines and isoquinolinones

The first Mannich reaction employing phthalides using a quinidine-based multifunctional catalyst has been developed. The reported method led to the synthesis of 3,3-disubstituted phthalide derivatives in excellent yields, with good diastereo- and enantioselectivities. Convenient synthesis of chiral isoquinolinones and isoquinolines has also been demonstrated.     

A facile access to mono-C-alkynylated-o-carboranes from o-carboranes and arylsulfonylacetylenes

A facile access to mono-C-alkynyl-o-carboranes from o-carboranes and arylsulfonylacetylenes was developed. This facile process tolerates a wide variety of functional groups, occurs at mild conditions in onepot procedure with short reaction time. The obtained mono-C-alkynyl-o-carboranes can be easily derivatized to synthesize 1,2-difunctionalized o-carboranes. This work provides a useful tool for the functionalization of o-carboranes.     

New chiral ligands and iron(III) complexes based on 2,6-bis(1-benzyl-4-isopropyl-4-methyl-4,5-dihydro-1H-imidazol-5-on-2-yl)pyridines

New ligands and their complexes with iron(III) chloride have been suggested and prepared: (R,S)-, (R,R)- and (S,S)-2,6-bis(1-benzyl-4-isopropyl-4-methyl-4,5-dihydro-1H-imidazol-5-on-2-yl) pyridines. Both the ligands and their complexes were characterised by ¹H and ¹³C NMR spectroscopy, optical rotation and X-ray diffraction.     

A facile and efficient procedure for the synthesis of new benzimidazole-2-thione derivatives

A series of benzimidazole-2-thione derivatives was synthesized using a reaction between the macrocyclic aminal 16H,13H-5:12,7:14-dimethanedibenzo[d,i]-[1,3,6,8] tetraazecine (DMDBTA, 5) and various nucleophiles in the presence of carbon disulfide. A full chemical characterization using IR, 1H-, 13C-NMR and GC-MS analyses of the new compounds is provided. These compounds were separated from the reaction mixture by column chromatography (CC) in highly pure form in 15%-51.4% yield.     

Asymmetrically induced alkylation of 2-benzyl-4-isopropyl-2,4-dihydro-1H-pyrazino[2,1-b]quinazoline-3,6-dione

The substitution of the 4-methyl group by a 4-isopropyl group in the 2-benzyl-2,4-dihydro-1H-pyrazino[2,1-b]quinazoline-3,6-dione system allows a notable improvement in the stereoselective alkylation at C-1. The configuration of the newly introduced stereogenic centre has been assigned on the basis of ¹H NMR data and NOE measurements.     

New distannanes containing the chiral 2-(4-isopropyl-2-oxazolinyl)-5-phenyl ligand

The N-coordinated tin hydrides containing the chiral 2-(4-isopropyl-2-oxazolinyl)-5-phenyl ligand in the presence of catalytic amounts of tetrakis(triphenylphosphine)palladium gave the corresponding distannanes in good yields. The distannanes have been fully characterized by means of the ¹H, ¹³C, ¹⁵N and ¹¹⁷Sn NMR measurements. The J(¹⁵N-^117/119Sn), J(¹¹⁷Sn-¹¹⁹Sn) couplings and single-crystal X-ray analysis of distannane 3 revealed a tendency towards penta-coordination at the tin center as a result of the Sn-N interaction.     

A facile and general route to 4-substituted-2 butenolides

Grignard reagents react with 7-oxabicyclo[2.2.1]hept-5-ene-2,3-dicarboxylic anhydride and produce in high yields the corresponding substituted bicyclo-γ-butanolides. These lactones produce the title compounds by retro Diels-Alder reaction during distillation.     

Stereoselective addition of the titanium enolate of N-acetyl (4S)-isopropyl-1,3-thiazolidine-2-thione to five-membered N-acyl iminium ions

[reaction: see text] Addition of the chlorotitanium enolate of N-acetyl 4-isopropyl-1,3-thiazolidine-2-thione to five-membered, N-substituted N-acyl iminium ions furnished the corresponding Mannich-type addition products with good diastereoselectivity and in good yields. The synthetic utility of the addition product 8 was demonstrated in a chemospecific anti-aldol reaction with cinnamaldehyde. By using this strategy, we constructed three contiguous chiral centers with high stereocontrol employing the same chiral auxiliary. X-Ray crystallographic analysis of addition product 2 and aldol product 14 revealed their absolute stereochemistry.     

A high-yielding low-cost facile synthesis of 2-oxazolidinones chiral auxiliaries

The chiral aminol alcohols from reduction of amino acids with NaBH₄/H₂SO₄ were directly treated with EtO₂CCl to give the carbamates, which cyclized in the presence of traces of K₂CO₃ at 100–130°C under vacuum to afford chiral 2-oxazolidinones in high yields.     

Highly enantioselective partial hydrogenation of simple pyrroles: a facile access to chiral 1-pyrrolines

A highly enantioselective Pd-catalyzed partial hydrogenation of simple 2,5-disubstituted pyrroles with a Br?nsted acid as an activator has been successfully developed, providing chiral 2,5-disubstituted 1-pyrrolines with up to 92% ee.     

A facile access to natural and unnatural dialkylsubstituted maleic anhydrides

A facile new route to the potential building blocks 2-bromomethyl-3-alkylmaleic anhydrides 15a/b for the synthesis of natural and unnatural dialkylsubstituted maleic anhydrides has been demonstrated, starting from dimethyl citraconate (9) via NBS-bromination, S_N2′ Grignard coupling reactions, hydrolysis, molecular bromine addition and dehydrative ring closure reactions pathway with 49-51% overall yield in 5-steps. Chemoselective allylic substitution of bromoatom in 15a/b with Grignard reagents has been described to obtain the unsymmetrical maleic anhydride 16 and symmetrically dialkylsubstituted maleic anhydrides 25a/b in 55% yield. The naturally occurring 2-carboxymethyl-3-hexylmaleic anhydride (1) has been synthesized from 16 via esterification, ozonolysis and an oxidation route. The synthesis of two naturally occurring 2-(β-carboxyethyl)-3-alkylmaleic anhydrides 2a/b have been completed via a chemoselective diethylmalonate coupling reaction followed by acid induced hydrolysis. In our hands the S_N2 or S_N2′ coupling of Grignard reagent with 21 to obtain 1 and Reformatsky reaction with 15a/b to obtain 2c/d met with failure.     

A novel heterobifunctional linker for facile access to bioconjugates

A convenient synthesis of a novel heterobifunctional linker molecule is described. The linker contains a thiol-reactive nitropyridyl disulfide group (Npys) and an aldehyde-reactive aminooxy group with a propensity to form disulfide and oxime linkages. The utility of the linker molecule to cross-link different biomolecules has been demonstrated by employing it in the efficient preparation of a peptide-oligonucleotide conjugate. The linker reported herein could be a useful tool for cross-coupling of different but appropriately functionalised biomolecules.