SEARCH Articles Figures Tables Cinchona Alkaloid Derivatives with a Sulfonamide, Urea, Thiourea, Squaramide, or Guanidine Function Guanidine-based thiourea derivative Guanidine-thiourea catalysis Guanidine-thiourea-based catalyst Guanidines and Thioureas Thiourea guanidine-based