Stereoselective benzylic α-acylamino radical cyclisation: a model study for the Tacaman indole alkaloid skeleton

Stereoselective tetrapyrido[2,1-a]isoindolone synthesis via carbanionic and radical intermediates: a model study for the Tacaman alkaloid D/E ring fusion

“…In the original study, 13 the chiral tether was derived from -ribose. The two stereogenic centres were cis-allylic and homoallylic to the enoate ester in the six-membered pseudochair transition state, and were considered to have opposing effects in controlling which chair conformation predominated.…”

“…Chemical shifts (δ) were recorded using residual chloroform (δ = 7.24 in 1 H NMR and δ = 77.00 in 13 C NMR) or tetramethylsilane as an internal standard. The residual DMSO peak (δ = 39.52 in 13 C NMR) was used as an internal standard for D 6 -DMSO solutions.…”

Synthesis of heterocycles by radical cyclisation

“…64, 65 In studies aimed towards the synthesis of the indole alkaloid tacamonine, the precursor 78 has been cyclised to yield the all cis tetrahydropyrido[2,1-a]isoindolone 79 stereoselectively as the major diastereomer (Scheme 20). 64 Several papers report the synthesis of bicyclic spiro amines. 43,66, 67 The methodologies shown in Scheme 15 using tandem cyclisation onto imines 43 and the protocol illustrated in Scheme 2 using xanthate transfer 66 have also been applied to the synthesis of spiroamines.…”

Recent developments in cyclization reactions of α-aminoalkyl radicals

“…The same strategy has been used in the formation of simpler aza- 20 and oxacycles 21 in 5-exotrig cyclizations, and similar additions have been performed on acylsilanes as well. 22 The corresponding 6-exo-trig cyclizations appear to be equally effective, as exemplified by the conversion of sulfide 20 and selenide 23 into tricycle 22 (Scheme 6) 23 and spirobicycle 25 (Scheme 7), 24 respectively. The latter was then converted into the alkaloid (-)-sibirine.…”