(2S,3R)-2-tert-Butoxycarbonylamino-3-(tert-butyl-dimethyl-silanyloxy)-pent-4-enoic acid methyl ester

[(4S,5S,6R)-5-tert-Butoxycarbonylamino-6-(2-hydroxy-ethyl)-2,2-dimethyl-[1,3]dioxan-4-yl]-acetic acid tert-butyl ester

[(4S,5R,6R)-5-tert-Butoxycarbonylamino-6-((Z)-2-methoxy-vinyl)-2,2-dimethyl-[1,3]dioxan-4-yl]-acetic acid tert-butyl ester

(4S,4aR,7aR)-4-tert-Butoxycarbonylmethyl-2,2-dimethyl-4a,7a-dihydro-4H-[1,3]dioxino[5,4-b]pyrrole-5-carboxylic acid tert-butyl ester