An easy α-glycosylation methodology for the synthesis and stereochemistry of mycoplasma α-glycolipid antigens

• Yoshihiro Nishida,
• Yuko Shingu,
• Yuan Mengfei,
• Kazuo Fukuda,
• Hirofumi Dohi,
• Sachie Matsuda and
• Kazuhiro Matsuda

Beilstein J. Org. Chem. 2012, 8, 629–639, doi:10.3762/bjoc.8.70

• . Syntheses of GGPL-I homologue I-a and its isomer I-b. Conditions: (a) K2CO3, CH3OH; (b) cesium palmitate in DMF; (c) TBDMS chloride then palmitoyl chloride in pyridine + DMAP; (d) TFA in CH3OH; (e) (i) 2-cyanoethyl-N,N,N’,N’-tetraisopropyl phosphorodiamidite, 1H-tetrazole and MS-4 Å in CH2Cl2; (ii) choline

Efficient, highly diastereoselective MS 4 Å-promoted one-pot, three-component synthesis of 2,6-disubstituted-4-tosyloxytetrahydropyrans via Prins cyclization

• Naseem Ahmed and
• Naveen Kumar Konduru

Beilstein J. Org. Chem. 2012, 8, 177–185, doi:10.3762/bjoc.8.19

• -tosyloxytetrahydropyrans was performed. The synthesis features an optimized Prins cyclization in which an aromatic homoallylic alcohol, an aromatic/aliphatic aldehyde, and p-toluenesulfonic acid (catalyst and reagent) are reacted in the presence of molecular sieves (MS) 4 Å at reflux in dichloromethane to afford excellent

• yields (72–96%) within short reaction times (20–90 min). The MS 4 Å-promoted synthesis proved to be versatile enough to provide an array of symmetrical and unsymmetrical tetrahydropyran derivatives in economical manner. Furthermore, cleavage of the 4-tosyl group under mild conditions afforded 4

• -hydroxytetrahydropyran in excellent yields (95–96%). Keywords: aromatic homoallylic alcohols; 2,6-disubstituted-4-tosyloxytetrahydropyrans; MS 4 Å; Prins cyclization; PTSA; Introduction Substituted tetrahydropyrans are common structural motifs in numerous biological molecules and natural products that include

A comparative study of the Au-catalyzed cyclization of hydroxy-substituted allylic alcohols and ethers

• Berenger Biannic,
• Thomas Ghebreghiorgis and
• Aaron Aponick

Beilstein J. Org. Chem. 2011, 7, 802–807, doi:10.3762/bjoc.7.91

• . Conditions: 5 mol % Au[P(t-Bu)2(o-biphenyl)]SbF6, CH2Cl2, MS 4 Å. Reaction progress in cis- and trans-methyl ethers. Conditions: 5 mol % Au[P(t-Bu)2(o-biphenyl)]SbF6, CH2Cl2, MS 4 Å. A comparison of commonly used protecting groups. Conditions: 5 mol % Au[P(t-Bu)2(o-biphenyl)]SbF6, CH2Cl2, MS 4 Å. Comparison

• of 1° and 2° allylic ethers. Conditions: 5 mol % Au[P(t-Bu)2(o-biphenyl)]SbF6, CH2Cl2, MS 4 Å. Au-catalyzed cyclization reactions of monoallylic diols. Reaction conditions for the preparation of 8. Supporting Information Supporting Information File 170: General procedures and characterization data