Die Halbsynthese des 6‐Hydroxy‐hyoscyamins)

Absolute Configuration of Natural Diastereoisomers of 6β-Hydroxyhyoscyamine by Vibrational Circular Dichroism

“…The bands assigned to the tropane ring vibrations clearly differentiate 1 from 2, showing that the absolute configuration of (+)-6β-hydroxyhyoscyamine ( 1) is (3R,6R,2′S), and that for the diastereoisomeric (-)-6β-hydroxyhyoscyamine ( 2) is (3S,6S,2′S), as previously reported. 12 It further follows that, since some early publications 17,18,20 are already amended, 21,22 verification of configurational assignments, either by chemical correlation or by VDC measurements, remains to be done in some cases. 15,16,[21][22][23][24] Experimental Section General Experimental Procedures.…”

“…The absolute configuration of tropane alkaloids of this type is commonly established using chemical correlation with the corresponding 3α,6β-tropanediol of known configuration. , The absolute configuration of 3α,6β-tropanediol was established , as (3 R ,6 R ) for the levorotatory free base ([α] D = −23.3) and (3 S ,6 S ) for the enantiomer ([α] D = +24.1) adopting the lactone rule of Hudson . Also, a levorotatory form of 6β-hydroxyhyoscyamine hydrobromide ([α] D = −10.5) was correlated with (+)-3α,6β-tropanediol hydrobromide ([α] D = +1.4) and assigned the (3 R ,6 R ) absolute configuration . The same authors corrected the absolute configurations of both enantiomeric 3α,6β-tropanediols by using chemical correlation with ( S )-methoxysuccinic acid, leading to the opposite conclusion. , Different articles concerning the isolation of (−)-6β-hydroxyhyoscyamine are found, most of which do not report specific rotation data.…”

“…19 Also, a levorotatory form of 6β-hydroxyhyoscyamine hydrobromide ([R] D ) -10.5) was correlated with (+)-3R,6βtropanediol hydrobromide ([R] D ) +1.4) and assigned the (3R,6R) absolute configuration. 20 The same authors corrected the absolute configurations of both enantiomeric 3R,6β-tropanediols by using chemical correlation with (S)-methoxysuccinic acid, leading to the opposite conclusion. 21,22 Different articles concerning the isolation of (-)-6β-hydroxyhyoscyamine are found, most of which do not report specific rotation data.…”