The C11-C22 and C23-C35 segments 2 and 3 of reidispongiolide A (1), an actin-depolymerizing marine macrolide, were synthesized enantioselectively in 12 steps from (R)-glycidyl trityl ether and in 12 steps from chiral ketone 15, respectively. (C) 2009 Elsevier Ltd. All rights reserved.