Reaction of 3 with (cyanomethylene)triphenylphosphorane in 8,9,10-trihydroxy-1-aza-6-oxaspiro[4.5]decane, which was identified as its peracylated derivative 16, was isolated. refluxing dichloromethane or methanol gave mixtures of 4a and 4b in ratios of about 3:1 and 1:3, respectively. The same Following an alternative synthetic strategy, partial hydrolysis of compound 9 afforded 17 which was regioselectively reaction performed with the furanoid isomer 5 afforded 6a and 6b in (E)/(Z) ratios of approximately 9:1 and 1:2, transformed into the corresponding derivative 22 via its 8-Op-toluenesulfonyl derivative 18. Removal of the 4,5-O-respectively. Catalytic hydrogenation of the α,β-unsaturated nitriles 4 and 6 with either 10% Pd-C or Raney nickel isopropylidene group in 22 with aqueous trifluroacetic acid gave the free octulose 23, which was hydrogenated in the afforded the saturated nitriles 7 and 9, or the 1-amino-1,2,3trideoxy-4-octulose derivatives 8 and 10, respectively. In an presence of 10% Pd-C, to afford the expected (6S,7R,8R,8aR)-6,7,8-trihydroxyindolizidine (1-deoxycasta-attempt to transform 6a into the appropriate polyhydroxylated branched-chain pyrrolidine 15, (5R,8S,9R,10S)-nospermine, 11).
[ ] Part IV: Ref. viously reported, [7] in which the stereoselectivity depended