The structural formula and crystal structure of the O-p-bromobenzoate derivative of batrachotoxinin A, C₃₁H₃₈NO₆Br, a frog venom and steroidal alkaloid

Abstract

Batrachotoxinin A, a venom from the Colombian poison arrow frog, Phyllobates aurotaenia, has been established by means of an X-ray analysis of the O-p-bromobenzoate derivative, to be 3e,9~-epoxy-14fl, 18/?-[epoxyethano-N-methylimino]-5/~-pregna-7,16-diene-3/?, 11~, 20~-triol. The material crystallizes in space group P21212a with a= 15.42, b = 7"05 and c= 26.50/~. The specialized position of the Br atom (at x, 0, 0) and the severely restricted amount of data limited the information which was available from use of the heavy atom phases. The structure was deduced by use of the tangent formula in a recycling procedure applied to partial structural information.

Bernhard Witkop (1917–2010)

“…Witkop’s interest in natural toxins led in 1963 to the isolation of batrachotoxin from a frog of the genus Phyllobates , which Columbian Indians use to prepare arrow poison 8. A new type of steroid alkaloid was resolved by X‐ray structure analysis in cooperation with Jerome and Isabella Karle 9…”

Bernhard Witkop (1917–2010)

“…Witkops Interesse an natürlichen Giften führte 1963 zur Isolierung des Batrachotoxins aus einem Frosch Phyllobates , aus dem kolumbianische Indianer ein Pfeilgift bereiteten 8. Ein neuer Typ von Steroidalkaloid wurde in Kooperation mit Jerome und Isabella Karle durch Röntgenstrukturanalyse geklärt 9…”

Configuration of the C(20) Epimer of 7,8-Dihydrobatrachotoxinin A

“…The isolation and characterization (1)(2)(3) of this venom has shown that the most toxic component is a steroidal alkaloid, batrachotoxin (Fig. 1A).…”