Optical resolution of 7‐oxabicyclo[2.2.1]hept‐21‐ene derivatives. Diastereoselectivity in the formation of cyanohydrine‐brucine complexes

Abstract

SummaryA new, practical method for the optical resolution of bicyclic ketones is illustrated by the preparation of (

Using ring-opening reactions of oxabicyclic compounds as a strategy in organic synthesis

“…The initial mixture of exo and endo cyanohydrins is equilibrated with base, resolved using brucine and acetylated to provide a 7:93 mixture of exo/endo cycloadducts. Successive recrystallizations of the initial crop afforded a 14% yield of the endo isomer (+)-4a of > 99% ee [12]. O 1.…”

Total synthesis of hydroxymethyl isonucleosides as potential antiviral agents

“…10 Ketone 9 was reduced stereoselectively to alcohol 10 by sodium borohydride in methanol in 65% yield from 8. 11 However, direct reduction of 8 with sodium borohydride gave even higher yields of 10 (89%) and with the same stereoselectivity.…”

“…1 H NMR (CDCl 3 ) (major isomer) δ 6.64 (dd, 1H, 10 To a solution of compound 8 (3.6 g, 20.09 mmol) in tetrahydrofuran-water (1:1, 100 mL) was added 1N sodium hydroxide (30 mL) at 0 °C. The resulting reaction mixture was stirred at 0 °C for 1 h and 37% formaldehyde (120 mL) was added to the reaction mixture, which was stirred at 0 °C for 10 min and extracted with chloroform (4 x 50 mL).…”

Regioselective Radical Additions to 7‐Oxabicyclo[2.2.1]hept‐5‐en‐2‐one

“…THF was freshly distilled from K under N,, CH2C1, from P,O,, and benzene from CaH, under N,. Irradiations were conducted using a sunlamp Osram Ultra-Vitalux 300 W. Compounds 1 (racemic) [14], 2 [lo] (CF,CO),O [I71 (29 ml, 208 mmol) was added dropwise to a soh. of the diamide (10 g, 71 mmol) and pyridine (22.6 ml, 280 mmol) in dioxane (100 ml) at -15O.…”