1: 40 percent / calcium alginate; citrate-phosphate buffer; aq. ammonia / glucose; Saccharomyces cerevisiae / ethanol / 24 h / 30 °C / pH 4.0 2: 86 percent / CaCl2; potassium carbonate / ethanol / 9.5 h 3: 98 percent / BF3*Et2O / 4 h / 20 °C 4: 98 percent / HCl / 1.5 h / 20 °C View Scheme