Conversion Of 1a Research Articles

A Convenient Reduction-Oxidation Procedure for the Selective Epimerization at Sulfur of Highly Functionalized, Optically Active Sulfoxides

Abstract A convenient method is described for the selective epimerizatin at sulfur of highly functionalized, optically active sulfoxides. The approach followed involves a sulfoxide reduction (with 2-phenylene phosphochloridite) - oxidation (with m-chloroperoxybenzoic acid) - separation of diastereomers sequence of steps. It was applied for the conversion of 3a, 3b and 3c into 2a, 2b and 2C, respectively, key intermediates in the total synthesis of the antitumor antibiotic sparsomycin and derivatives. Overall yields range from 26% to 37%.

Aromatic Nucleophilic Nitrogen-Nitrogen Exchange Reaction ofN,N-Dimethyl-2,4-bis(trifluoroacetyl)-1-naphthylamine with Amino Acid Derivatives: A Facile Synthesis of Fluorine-Containing 1H-Benzo[g]indolines and 1H-Benzo[g]indoles

Aromatic nucleophilic nitrogen-nitrogen exchange reaction of N,N-dimethyl-2,4-bis(trifluoroacetyl)-1-naphthylamine 1 with some amino acid derivatives gives the corresponding N-[2,4-bis(trifluoroacetyl)-1-naphthyl]amino acid derivatives 2a-d in excellent yields. Basecatalyzed cyclization affords fluorine-containing 1H-benzo[g]indolines (2,3-dihydro-1H-benzo[g]indoles) 3a-d in high yields. Further conversion of 3a into 1H-benzo[g]indoles 4,5 is also described.

Nucleic acid related compounds. 34. Non-aqueous diazotization with tert-butyl nitrite. Introduction of fluorine, chlorine, and bromine at C-2 of purine nucleosides

Treatment of 2,6-diamino-9-(2,3,5-tri-O-acetyl-β-D-ribofuranosyl)purine (1c) with tert-butyl nitrite (TBN) in 60% anhydrous hydrogen fluoride/pyridine at −20 °C gave 2-fluoroadenosine triacetate (2) in 48% yield. Analogous treatment of the acetylated 2-amino-6-fluoropurine nucleoside (1a) gave the 2,6-difluoro compound (3a) in 63% yield. Anhydrous ammonia in 1,2-dimethoxy-ethane converted 3a → 2 without ammonolysis of the acetate groups. The overall conversion of 1a → 3a → 2 without isolation of 3a proceeded in 80% yield. Similar diazotization of the 2-amino-6-chloro nucleoside (1b) in HF/pyridine gave the 2-fluoro-6-chloro analogue (3b) in 89% yield. Treatment of 1b with TBN and pyridine hydrochloride in dichloromethane (77%) or TBN and antimony trichloride in 1,2-dichloroethane (84%) gave the 2,6-dichloropurine nucleoside (4b). The latter conditions converted 1a to the 2-chloro-6-fluoro product (4a) in 77% yield. Conversions of 1a and 1b to the 2-bromo-6-fluoro (5a, 67%) and 2-bromo-6-chloro (5b, 78%) analogues were effected using TBN and antimony tribromide in dibromomethane.