Guilong Zhao

A facile approach to indolizines via tandem reaction

Indolizines were synthesized by a novel tandem reaction at rt. The operation was simple and convenient. Various indolizine derivatives were obtained in good yields. The reaction mechanism was also proposed.

Total Synthesis of α-Elvucitabine

Abstract Total synthesis of α-elvucitabine was achieved in 26% overall yield by a concise nine-step procedure starting from L-lyxose, with trimethylsilyl trifluoromethaneoulfonate (TMSOTf)–mediated stereocontrolled α-N-glycosidation and olefination through Barton–McCombie deoxygenation being the key steps, and the stereochemistry of the product was determined by nuclear Overhauser effect spectroscopy. GRAPHICAL ABSTRACT

Polyphosphoric Acid–Mediated, One-Pot, Novel Reactions to Build Polymethoxyarylnaphthalene Lignans

The one-pot reaction of succinic anhydride with 1,2-dimethoxybenzene furnished two structurally complicated polymethoxyarylnaphthalene lignans, polymethoxyarylnaphthol 1 as the minor product and polymethoxynaphtho[1,2-b]oxacycloheptatrienone 2 as the major product, in the presence of a small amount of polyphosphoric acid (PPA) as catalyst at 140°C and yielded 2 as a single product in good yield when a large amount of PPA as solvent was employed at 60–80°C. The novel structures of 1 and 2 were elucidated from 1H NMR, 13C NMR, infrared (IR), and Electrospray ionization–mass spectrometry (ESI-MS) and further confirmed by x-ray diffractions. The possible mechanisms for the formation of 1 and 2 were also proposed.

Total Synthesis of 4″‐O‐Acetylmananthoside B, Part I: Synthesis and Tentative Ozonolysis of a Cyclohexadiene Derivative

Abstract A cyclohexadiene derivative cis‐N,N‐diethyl‐2‐benzyloxymethyl‐1,2‐dihydrobenzamide 8 was constructed from γ‐butyrolactone I for the total synthesis of a natural product 4″‐O‐acetylmananthoside B, which was reported to display significant cytotoxic activity. Preliminary ozonolysis of 8 for further synthetic purposes was also carried out.

2,3-Dihydro-1,5-benzothia­zepin-4(5H)-one

The title compound, C9H9NOS, crystallizes with two independent molxadecules in the asymmetric unit. The bond lengths and angles in both molxadecules are within normal ranges. The crystal packing is stabilized by interxadmolecular N—H⋯O hydrogen bonds and van der Waals forces.

Ethyl 6-methyl-sulfanyl-2-phenyl-1H-imidazo[1,2-b]pyrazole-7-carboxyl-ate monohydrate.

The title compound, C15H15N3O2S·H2O, has been obtained in a search for new imidazo[1,2-b]pyrazole derivatives with better biological activity. The 1H-imidazo[1,2-b]pyrazole plane forms a dihedral angle of 16.90u2005(3)° with the benzene ring. π–π interactions are indicated by the short distance of 3.643u2005(2)u2005Å between the centroids of the benzene and imidazole rings. The crystal structure also involves intermolecular O—H⋯N hydrogen bonds.

Ethyl 6-methyl-2-p-tolyl­pyrazolo[1,5-a]pyridine-5-carboxyl­ate

In the title molecule, C18H18N2O2, the bicyclic ring system and the benzene ring form a dihedral angle of 13.45u2005(3)°. In the crystal structure, weak intermolecular C—H⋯O hydrogen bonds link molecules into chains propagated along [201].

tert-Butyl N-(5-bromo-1H-imidazo[4,5-b]pyridin-2-ylmeth­yl)carbamate

In the molecule of the title compound, C12H15BrN4O2, the imidazole and pyridine rings are strictly coplanar [maximum deviation 0.006u2005(3)u2005Å]. In the crystal structure, molecules are linked into chains running parallel to the a axis by intermolecular N—H⋯O hydrogen bonds. Centrosymmetrically related chains are further connected by N—H⋯N hydrogen-bonding interactions to form a two-dimensional layer structure parallel to the ab plane.

4-Methoxy­phenyl 2,3,4,6-tetra-O-acetyl-β-d-galactopyran­oside

The six-membered sugar ring of the title compound, C21H26O11, adopts a chair conformation. The crystal structure is stabilized by interxadmolecular C—H⋯O hydrogen bonds and van der Waals forces.