4-Ethoxycarbonylethyl curcumin (ECECur) (3) is a current drug candidate for the treatment of prostate cancer. Due to problems inherent in the tautomerism of ECECur, 4-fluoro-4-ethoxycarbonylethyl curcumin (4) and 4-ethoxycarbonylethylenyl curcumin (5) were designed and synthesized. These two target compounds and their synthetic intermediates (4-9) were evaluated for their inhibitory activity against androgen receptor transcription in LNCaP and PC-3 prostate cancer cell lines. While the enol-keto analogs showed varying anti-androgen potencies, the di-keto analogs showed no activity. Tetrahydropyranylation of the phenoxy groups had a positive impact on the anti-AR activity of 4-ethoxycarbonylethylenyl curcumin, but a negative impact on the activity of ECECur. With potent anti-AR activity, di-tetrapyranylated 4-ethoxycarbonylethylenyl curcumin (9), which exists in only one form, is a good drug lead for further structural modification. Based on the SAR information obtained from the above study, five new compounds were designed and subsequently synthesized. Among them, compound 10 was found to be the most potent anti-AR agent and is considered to be a promising drug candidate for the treatment of prostate cancer.