Syntheses of compounds 34a, b and 37-40. Reagents and conditions: a) 12a or 12b, prop-2-yn-1-yl N-(prop-2-yn-1-yl)carbamate, sodium L-ascorbate, copper (II) sulfate pentahydrate, H2O-tert-BuOH 1:1, rt, 3h; b) prop-2-yn-1-amine, sodium L-ascorbate, copper (II) sulfate pentahydrate, H2O-tert-BuOH 1:1, rt, 3h; c) prop-2-ynyl chloroformate, Et3N, dry DCM, 0 °C, 30 min; d) 12a or 12b, sodium L-ascorbate, copper (II) sulfate pentahydrate, H2O-tert-BuOH 1:1, rt, 3h.