Conformational equilibria in quinolizide and indolizidine systems

Optical rotatory dispersion and absolute configuration. Part 35. Chiroptical properties and conformation of indolizidine

“…Although cis-and trans-fused isomers of hydrindane (bicyclo[4.3.0]nonane) and its substituted derivatives are well known,' corresponding stereoisomers of (1) cannot be isolated because rapid inversion of configuration at nitrogen interconverts them, producing an equilibrium mixture. In the studies of this equilibrium in (1) and its derivatives special attention has been given to the Bohlmann bands in the i.r. spectrum, which are obtained when two or more a-hydrogen atoms are trans diaxial to the lone electron pair of n i t r ~g e n .…”

“…spectrum, which are obtained when two or more a-hydrogen atoms are trans diaxial to the lone electron pair of n i t r ~g e n . ~ This criterion is satisfied by (1) only when the rings are trans-fused. The i.r.…”

A Reinvestigation of the Oxidative Rearrangement of Yohimbane‐Type Alkaloids. Part A. Formation of pseudoindoxyl ( = 1,2‐dihydro‐3H‐indol‐3‐one) derivatives

“…HETCOR: 153,717.47;129.917.37;126.1/7.20;122.3/7.41;121.6/?.62;73,314.36;60.5/3.05;56.912.93,2.19;51.0/3.71;50.0/2.75,2.71;40.9/2.02;35.912.74,1.48;30.3/3.08,1.77;30,012.33;21.0/2.07;14.8/1.16. MS: 410 (3, M'), 379 (59, 350 (loo), 209 (12), 184 (12), 169 (14), 156 (19), 130 (13), 115(10),77 (14), 55 (27),43 (25),42 (24),41 (11).…”

“…HETCOR: 136.917.40;124.6/7.54;118.8/6.78;111.8/6.79;79.2/2.20;66.714.11;58.7/3.10,1.80;53.313.33,2.36;52.212.22;51.5/3.52;39.611.45;36311.68;35.2/2.38,1.87;31.2/1.92,1.45;29.4/ 1.17;23.411.45,1.36. MS: 370 (17,M+), 225 (38), 224 (loo), 130 (11). 1162,1119,1076,1015,1010,952.…”

Epimeric 1‐hydroxy‐1‐substituted indolizidines

“…Epinrers Ic and IIc arc: analogs of e p h d r i n r (3a), w1ic:rcas the methiodides of the acetates of Ib and 1% arc analogs of methac:holint: (3b). Aaron (4,5,6) nott:d that trans ring fusion is thi: pretloininant conformation for both thc: axial hydroxy and tht. quatorial hydroxy cpimers of I-, 2-, 7-, and 8hy droxy indolizidiiws.…”