The cyclopropenation of diethoxypropyne (1) with methyl diazoacetate in the presence of [Rh₂{(2S)‐mepy}₄] (mepy=methyl 5‐oxopyrrolidine‐2‐carboxylate) proceeds with >95% ee. The resulting cyclopropenecarboxylate 2 underwent stereoselective hydrogenation to the cis‐cyclopropane 3. Hydrolysis of the acetal function of 3 liberated the formyl cyclopropenecarboxylate 4, which was transformed by Wittig reaction with the phosphonate 5 to afford dehydroamino acid 6 as a mixture of (Z)‐ and (E)‐isomers in various proportions. The (Z)‐isomer 6a was hydrolyzed, and the structure and the absolute configuration of the (Z)‐dicarboxylic acid 7a were established by X‐ray crystallography. The cis‐divinylcyclopropane 11 (ee>95%), in turn, was synthesized from 4 via Wittig reaction to afford 8, which was transformed to the aldehyde 10 and subjected to a second Wittig reaction. Thermolysis of 11 afforded (+)‐dictyopterene C′ (12) in quantitative yield.