Kerekgyarto, Janos; Agoston, Karoly; Batta, Gyula; Kamerling, Johannis P.; Vliegenthart, Johannes F. G. Tetrahedron Letters, 1998, vol. 39, # 39 p. 7189 - 7192 doi: 10.1016/S0040-4039(98)01540-8