The synthesis of octosyl nucleosides based on intramolecular oxyselenation of a conjugated diene
摘要:
A new stereoselective ring construction for 3,7-anhydrooctofuranosyl nucleoside, which is based on a 6-endo-trig oxyselenation of a conjugate diene, (5'S)-C-(4-phenyl-1,3-butadienyl)uridine, was developed. Because of the appropriate array of Functionalities at the 5', 6', and 7'-positions, the cyclization product 14 can be considered to be a versatile synthon for the synthesis of a series of octosyl nucleoside antibiotics. Factors governing the efficiency of this cyclization are also discussed. (C) 1998 Elsevier Science Ltd. All rights reserved.
Intramolecular radical reaction of 2′,3′-O-isopropylideneuridine 5′-monoselenoacetal 6 appeared to result in reverse stereoselectivity to that of the corresponding 5′-aldehyde (3). Intermolecular version of this reaction by using allyltributylstannane as a radical acceptor showed preferential anti-Cram diastereoface selection.