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4‐Octulose Derivatives, Prepared from L ‐Sorbose, as Key Intermediates in the Stereoselective Synthesis of C ‐Glycoside and Polyhydroxyindolizidine Analogues
Author(s) -
Izquierdo Isidoro,
Plaza Maria T.,
Robles Rafael,
Mota Antonio J.
Publication year - 2000
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/1099-0690(200006)2000:11<2071::aid-ejoc2071>3.0.co;2-a
Subject(s) - chemistry , glycoside , stereoselectivity , dichloromethane , yield (engineering) , methanol , pyridine , chloride , anhydrous , imidazole , dihydroxylation , stereochemistry , organic chemistry , catalysis , solvent , materials science , metallurgy , enantioselective synthesis
Reactions of 1 and 12 with p ‐toluenesulfonyl chloride in pyridine gave the corresponding 1‐ O ‐ p ‐toluenesulfonyl derivatives 2 and 13 in yields of 91% and 60%, respectively. Compound 12 was also transformed into 14 by treatment with I 2 /Ph 3 P/imidazole in anhydrous dichloromethane. Treatment of compounds 12 and 13/14 with NaN 3 in DMF furnished the respective 1‐azido‐1‐deoxy derivatives 3 and 15 , which were then deacetonated to give the free 4‐octuloses 4 and 16 . These were subsequently hydrogenated in the presence of 10% Pd/C to afford the expected polyhydroxylated branched‐chain pyrrolidines 5 and 17 . Attempted OH → OMes transformation at C‐8 in the N −Cbz‐protected pyrrolidines 7 and 19 was unsuccessful and an internal anhydration process took place to yield the corresponding C ‐glycoside‐like furanoses 9 and 20 . On the other hand, 23 was transformed into the D ‐ ribo analogue 25 through reduction of the intermediate 4,6‐diulose 24 . Finally, deprotection of 25 in acid medium to give the free 4‐ulose 26 , followed by hydrogenation of the latter in the presence of 10% Pd/C in methanol, allowed the preparation of (6 S ,7 S ,8 S ,8a S )‐6,7,8‐trihydroxy‐8a‐methoxyindolizidin‐3‐one ( 27 ).