Novel efficient synthesis of 1-ethoxyvinyl esters using ruthenium catalysts and their use in acylation of amines and alcohols: synthesis of hydrophilic 3′-N-acylated oxaunomycin derivatives

Abstract

A novel and efficient synthesis of 1 -ethoxyvinyl esters 3a-i from carboxylic acids 4a-i and ethoxyacetylene 5 by using a catalytic amount of ruthenium complex [{RuCI,( p-cymene)},] 6f has been developed. These reagents reacted smoothly with amines and alcohols to give the corresponding N -and 0-acylated compounds in excellent yields. This acylation method has been applied to the synthesis of hydrophilic 3'-N-acylated oxaunomycin derivatives 13a, b.

Recent developments in chiral non-racemic sulfinyl group chemistry in asymmetric synthesis

“…The use of an O-silylated ketene acetal as activating agent has been introduced in 1984. 189 This area has received a lot of attention in the last 20 years, 190 and only the most recent developments will be covered here. The main advances in this area have been made by the group of Kita, and their most notable results have been reviewed in 1996.…”

Kinetic Resolution of 1-Biaryl- and 1-(Pyridylphenyl)alkan-1-ols Catalysed by the Lipase B fromCandida antarctica

“…Although acetone could also form a hemiacetal with 6, the hydroxy group of this compound would be analogous to that of a tertiary alcohol, with CAL-B not showing any transesterification activity towards this kind of substrate. [18] When 1-ethoxyvinyl acetate [19] was employed as acyl donor in the reaction with rac-6o ( Table 2, entry 3), no side products were detected, but the reaction was slower and less enantioselective than when vinyl acetate was used. This lower enantioselectivity may be due to a competitive, non-enzymatic acylation of the alcohol as a consequence of the long reaction time.…”

“…COSY, HSQC and HMBC experiments were carried out using standard Bruker software. For the determination of some enantiomeric excess values, 19 F NMR spectra of the corresponding diastereomeric pair of Moshers esters were obtained with a Bruker AV-300 spectrometer (282.38 MHz); the diastereomeric ratio was determined from the inverse-gated protondecoupled 19 F NMR spectra of the crude reaction mixture, using a pulse width of 158, a relaxation delay of 10 s and an accumulation of 240 -4096 scans. Most of the enantiomeric excesses were determined with an LC-10AD Shimadzu high performance liquid chromatograph, using Chiralcel OD or OB-H columns (Daicel).…”

Total syntheses of bioactive natural products from carbohydrates

“…Each of the four hydroxyl groups of 113 was discriminated from others. Lactonization of 114 was tested under the various conditions to construct C-D ring and the best result was realized by using Kita's conditions [117] to afford the d-lactone 115 which possessed another 10 membered lactone ring. The allylic alcohol of the lactone 115 was oxidized to a,b-unsaturated ketone 116 by exposure to MnO 2 .…”

“…The stereochemical array of the northern part was derived from L-arabinose (117). Lactone 118 [123] was submitted to the stereoselective methylation and reductive ring opening to give diol 120, possessing functionality to be the northern part 121.…”