The structure of ervincidine

Stereospecific Total Synthesis of the Indole Alkaloid Ervincidine. Establishment of the C-6 Hydroxyl Stereochemistry

“…The optical rotation of this diastereomer 2 was determined to be [α] D 26 +79° ( c 0.6, MeOH), which was not in agreement with the value reported in the literature. 3 − 5 Hence, the diastereomer 2 was stirred in 0.2 N HCl at 0 °C. Examination by TLC (silica gel; CH 2 Cl 2 :MeOH 9:1) indicated a new component at a lower R f value, which illustrated that complete epimerization of the alcohol function at C-6 to diastereomer 2′ had occurred.…”

“…To achieve the synthesis of the diastereomer with the C-16 hydroxymethyl function in the β position as proposed by Yunusov et al, 3 , 4 pentacyclic ketone 4 was treated with triphenylphosphonium bromide in benzene in the presence of potassium t -butoxide to afford diene 10 in 90% yield (Scheme 2 ). 17 To facilitate attack on diene 10 from the less hindered face of the exocyclic methylene function and prevent hydroboration of the C(19)–C(20) olefinic bond, 18 9-BBN was chosen as the hydroborating agent.…”

“…Yunusov et al, 3,4 who isolated this alkaloid, had reported the structure of ervincidine as similar to that of the polyneuridine subclass with four stereocenters, C-3 ( S ), C-5 ( R ), C-15 ( R ), and the hydroxymethyl function in the β configuration at C-16 ( S ). However, the stereochemistry of the C-6 alcohol was not assigned in this report as well.…”

Indole alkaloids from Vinca erecta type of sarpagine and ajmaline

“…The reference book [5] notes the isolation of five indole alkaloids of the sarpagine type from V. erecta (according to the systematics of Lee Men [7]): tombosine [8], 6-hydroxytombosine (ervincidine) [9], o-benzoyl-tombosine [10], 10methoxy-alkyllosimine [11] and akuammidine [12], which differ in exo-substituents in the sarpagine skeleton ( Figure 1). In tombosine, the carbon atom C22 is absent, but the polycyclic skeleton of sarpagin remains.…”

“…The sarpagine and ajmaline groups have a 3D polycyclic framework and a two-dimensional representation of the structure, indicating the relative α-or β-orientation of the substituent is difficult. For example, due to the fuzzy reduction of the chemical structure of ervincidine [9], it was mistakenly accepted as 16-epi-6-hydroxy tombosine in the 2010 reference book [20], although later its structure was corrected for 6hydroxy tombosine [5]. For this reason, in determining the absolute configuration, the values of the chirality descriptors R, S are the main addition in the description of the asymmetric center.…”