Stereoselective hydrogenation and ozonolysis of iridoids. Conversion into carbocyclic nucleoside analogues

Stereoselective hydrogenation of the iridoids geniposide (9) and aucubin (1 9) was achieved by using the 1-methyl-1-methoxyethyl ether as a protecting group for the allylic alcohol, as it enhanced the stereoselectivity and pre vented undesired hydrogenolysis. Ozonolysis of the hydrogenation product fr om 9, adoxoside (11), with reductive workup, afforded either a chiral lacto ne (25) or a chiral polyol (26), depending on the reduction conditions. Pol yol 26 was subjected to protecting-group manipulation and subsequent oxidat ion and reductions to yield cyclopentane building blocks (29-34), which, by Mitsunobu couplings with purines, afforded carbocyclic nucleoside analogue s (7, 8, and 35).