Intramolecular amidomercurations under allylic control: a stereoselective synthesis of (+)-pseudohygroline and (+)-3-hydroxypyrrolizidine

Hydroamination: Direct Addition of Amines to Alkenes and Alkynes

“…559,560 The alkaloid pseudohygroline was prepared by mercuration of compound 314 followed by radical reduction giving the pyrrolidine 315, a direct precursor of the natural product (Scheme 137). 561 Tackas et al described the use of an amidal as a removable auxiliary in amidomercuration reactions. For instance, compound 316 was successively mercurated and reduced to give almost exclusively the corresponding endo,trans-317 (less than 0.5% of the exo,cis-isomer) as a protected form of the corresponding amino alcohol (Scheme 138).…”

“…The alkaloid pseudohygroline was prepared by mercuration of compound 314 followed by radical reduction giving the pyrrolidine 315 , a direct precursor of the natural product (Scheme ) …”

Pyrrolizidine alkaloids

“…A synthesis of the simple 2-hydroxypyrrolizidine 277 (reported as the 3-isomer) 115 was cyclised to organomercurial 276 with dr > 10 : 1. Following reductive demercuration, acetonide cleavage, and activation of the 1 -alcohol as the mesylate, hydrogenolysis released the free amine which cyclised giving the mesylate salt of (+)-2hydroxypyrrolizidine.…”