Scheme 2. Optimised synthetic route for the orthogonally protected (Me)Lan building blocks 6 and 7. Reagents and conditions: (a) Boc₂O, NaOH, RT, 12 h; (b) Allyl-Br, Cs₂CO₃, DMF, RT, 12 h; (c) TFA, CH₂Cl₂, RT, 2 h; (d) Trt-Cl, Et₃N, EtOAc, 0–25 °C, 12 h; (e) MsCl, CH₂Cl₂, 0–25 °C, 12 h; (f) Et₃N, DMF, 70 °C, 12 h; (g) TFA, CH₂Cl₂, MeOH, 0 °C, 2 h; (h) DNS-Cl, Na₂CO₃, EtOAc, RT, 12 h; (i) Fmoc-Cys-OH, BF₃·OEt₂, CH₂Cl₂, 0–25 °C, 72 h; (j) thioglycolic acid, Et₃N, CH₂Cl₂, 0 °C, 2 h; (k) Alloc-Cl, NaHCO₃, H₂O, dioxane, 0–25 °C, 12 h. Alloc, allyloxycarbonyl; Trt, triphenylmethyl; DNS, 2,4-dinitrobenzenesulfonyl.