“…Given the relative stability of 3a-fluoro-indolines , compared to other 3a-halo-indolines, , we opted for electrophilic fluorocyclization of 4 (Figure ) to create 3a-fluoro-6-MIDA-boronyl-1,2,3,3a,8,8a-hexa-hydropyrrolo-[2,3- b ]indolyl- N α -Boc-2-carboxylate ( 5 ). Although fluorocyclization of tryptophan derivatives is known, , the feasibility of converting a 3a-fluoro-indoline to a tryptathionine cross-link is unprecedented . Following desilylation and de-esterification, 1 was converted to MIDA-boronate ester 4 , which gratifyingly fluorocyclized cleanly in the presence of 1-fluoro-2,4,6-trimethylpyridinium triflate to afford 5 as an inseparable pair of diastereomers ( syn-cis and anti-cis ) in 85% yield (Scheme ).…”