A common, divergent, and efficient approach to the syntheses of (+)-steviamine (9), (–)-1-deoxy-8a-epi-castanospermine (10), (+)-trihydroxyindolizidine (11), (+)-3,7a-di-epi-hyacinthacine A1 (12), and (–)-2-epi-lentiginosine (4) was achieved by starting from D-ribose-derived intermediate 13. The key steps involved in these syntheses are a highly diasteroselective Grignard addition to a ribosylimine