The planar structure of poecillastrin C (1) was revised through selective reduction of the ester carbon. The absolute configuration of the β-hydroxyaspartic acid (OHAsp) residue was determined to be d-threo by Marfey's analysis. The acid hydrolysate of the reduction product of 1 liberated (2R,3R)-2-amino-3,4-dihydroxybutanoic acid, demonstrating that the β-carboxyl group in poecillastrin C was esterified. The structures of poecillastrins B-D and 73-deoxychondropsin A were also revised.