摘要:
Stereoselective hydrogenation of the iridoids geniposide (9) and aucubin (19) was achieved by using the 1-methyl-1-methoxyethyl ether as a protecting group for the allylic alcohol, as it enhanced the stereoselectivity and prevented undesired hydrogenolysis. Ozonolysis of the hydrogenation product from 9, adoxoside (11), with reductive workup, afforded either a chiral lactone (25) or a chiral polyol (26), depending on the reduction conditions. Polyol 26 was subjected to protecting-group manipulation and subsequent oxidation and reductions to yield cyclopentane building blocks (29-34), which, by Mitsunobu couplings with purines, afforded carbocyclic nucleoside analogues (7, 8, and 35).