Bromoacetal 2 undergoes a novel ring-contracted reaction to give the aldehyde 3 in the presence of DBU or triethylamine. The aldehyde 3 is reduced to the alcohol 4 and oxidized to the carboxylic acid 5. The alcohol 4 reacts with dihydroartemisinin to give the two diastereoisomers 38 and 39. All the compounds were tested for antimalarial activity in mice infected with chloroquine sensitive Plasmodium berghei. If the activity of a compound was comparable to that of the standard compound, such as arteether, it was tested against chloroquine resistant NS strain infection in mice. Initially the compounds were administered subcutaneously, and if found to be active, they were tested by oral route. The antimalarial activity of compounds 19, 38, and 39 was found to be comparable to that of arteether when tested in K-173-infected mice. They were also active against chloroquine resistant NS strain infection in mice.