Syntheses are reported for gamma-glutamyl Se-methylselenocysteine (Sa), selenolanthionine (16), Se-1-propenylselenocysteine (Gd), Se-2-methyl-2-propenyl-L-selenocysteine (6e), and Se-2-propynyl-L-selenocysteine (6f). Oxidation of 8a and Se-methylselenocysteine (Ga) gives methaneseleninic acid (24),