Scheme 1. Reagents and conditions: (a) TsCl, Et₃N, Me₃N·HCl, CH₂Cl₂ (99%); (b) HSCH₂CH₂OH, NaH, DMF, 100 °C (93%); (c) BnBr, NaH, DMF, 0 °C (32: 90%, 41: 99%); (d) HFIP, K₂CO₃, reflux (34: 96%, 42: 95%); (e) H₂, Pd–C, 10% aq. TFA, 1,4-dioxane, 50 °C (26a: 94%, 28a: 93%); (f) 5% methanolic HCl, (26b: rt, 92%, 28b: 50 °C, 88%); (g) IRA-400J (Cl⁻ form), CH₃OH, rt (26c: 93%, 28c: 87%, 39: 98%); (h) HSCH₂CH₂OH, K₂CO₃, C₂H₅OH, reflux (99%); (i) HBF₄·(C₂H₅)₂O, CH₂Cl₂, −78 °C (71%); (j) H₂, Pd–C, CH₃OH, rt (89%).