A practical route to partially protected pyrrolidines as precursors for the stereoselective synthesis of alexines.
Either 3-O-benzoyl- (2a) or 3-O-benzyl-1,2-O-isopropylidene-beta-D-fructopyranose (2b) were regioselectively O-benzylated at C-4 to give 4a and 4b, respectively, which were transformed into 5-azido-3-O-benzoyl-4-O-benzyl- (6a) and 5-azido-3,4-di-O-benzyl-5-deoxy-1,2-O-isopropylidene-alpha-L-sorbopyranose (6b) by nucleophilic displacement of the corresponding 5-O-mesyl derivatives 5a and 5b by sodium azide in DMF, respectively. Compound 6b was also prepared from 4b in one step by the Mitsunobu methodology. Deacetonation of 6a and 6b gave the partially protected free azidouloses 8a and 8b, respectively, that were protected as their 1-O-TBDPS derivatives 9a and 9b. Hydrogenation of 9b over Raney nickel gave stereoselectively (2R,3R,4R,5S)-3,4-dibenzyloxy-2'-O-tert-butyldiphenylsilyl-2,5-bis(hydroxymethyl)pyrrolidine (12) which was identified by transformation into the well known (2R,3R,4R,5S)-3,4-dihydroxy-2,5-bis(hydroxymethyl)pyrrolidine (1, DGDP).
Cubero
I I
II
Department of Organic Chemistry, Faculty of Pharmacy, University of Granada, Spain. isidoro@platon.ugr.es
López-Espinosa
M T
MT
Díaz
R R
RR
Montalbán
F F
FF
D002236:Carbohydrate Conformation; D005632:Fructose / Q000138:chemical synthesis* / Q000737:chemistry; D007202:Indicators and Reagents; D008958:Models, Molecular; D009904:Optical Rotation; D011759:Pyrrolidines / Q000138:chemical synthesis* / Q000737:chemistry*; D013237:Stereoisomerism; D013329:Structure-Activity Relationship
D007202:Indicators and Reagents; D011759:Pyrrolidines; D005632:Fructose