In previous work, a new class of synthesized bioactive compounds of Morita –Baylis-Hillman adducts (MBH) showed an antioxidant and anti melanogensis activity. Accordingly, in the present work the relationship between antifungal activity and the responsible chemical function of MBH adducts and their derivatives (alcohols, acetates, phosphonates and hydrazono phosphonates) was investigated against plant pathogenic fungi Aspergillus niger, Fusarium oxysporum, Penicillium occitanis, Trichoderma reesei, Stachybotrys microspora, Fusarium solani, Trichoderma parceramosum, fusarium aethiopicum, Alternaria alternata and Aspergillus flavus using the agar diffusion method. Results showed acetates displayed varying degrees of antifungal activity against several fungi tested, while just one alcohol compound showed lower activity. The derivative with five carbon (2g) was the most powerful with an inhibitor growth zone diameter of 4.75÷0.21, 6.1±0.14, 4.35±0.21, 3.9±0.14, 4.54± 0.11, 3.55±0.07, 3±0, 3.2± 0.2, 5.36 ± 0.26 and 5.06± 0.5cm against; F. oxysporum, T. parceramosum, S. microspora, T. reesei, F. solani, P. occitanis, A. niger, F. aethiopicum, A. alternate and A. flavus respectively. Compared to the positive control the nystatin, most of the tested compounds exhibited moderate to strong inhibitory effects. The antifungal activity depended on the radical group. The novelty is that these adducts are evaluated for the first time for their antifungal effect. Antifungal activity is in general of linear or cyclic molecules coupled to six carbons. Here we show that the simple acetate six membered carbons are the most efficient molecule