The major physiological function of hemoglobin (Hb) is to bind, transport and deliver oxygen to tissues; made efficient by endogenous effectors, such as protons and 2,3-diphosphoglycerate. Synthetic allosteric effectors of Hb (AEHs) are also known to modulate Hb oxygen affinity, showing potential for the treatment of sickle cell disease (SCD) and ischemic-related diseases. In this project, AEHs which increase Hb affinity for oxygen, including derivatives of the anti-sickling compounds, 5HMF and benzaldehydes, as well as an AEH that decreases Hb affinity for oxygen, RSR-13, were synthesized for their effects on Hb oxygen binding property and their capability to release NO from substituted nitrate ester moieties. Compounds that were found to increase Hb affinity for oxygen were further tested for their anti-sickling activities. Structural studies were carried out to gain insight into the compound’s mode of action. Development of these agents could be a therapeutic strategy for SCD or ischemic-related diseases.