Digoxin dialdehyde reductive aminations. Structure proof of the perhydro-1,4-oxazepine product

Digoxin dialdehyde reportedly undergoes reductive amination with primary amines to form a perhydro-1,4-oxazepine; however, no structural proof has been published to substantiate this belief. A digoxin perhydro-1,4-oxazepine derivative has been isolated from the reductive amination of digoxin dialdehyde and its structure determined by mass spectroscopy and NMR measurements. Comparison of the NMR, mass spectroscopy, and HPLC of two compounds obtained from the degradation of the digoxin reductive amination product with synthesized perhydro-1,4-oxazepine diastereomers showed them to be identical. We conclude that, under appropriate conditions, reductive amination products can be obtained, but caution that other products may be produced as well, especially under the conditions of bioconjugation to proteins.

Determination of femtomol quantities of gibberellic acid by radioimmunoassay

A highly sensitive and specific radioimmunoassay which allows the detection of as little as 5 fmol (2 pg) of gibberellic acid (GA3) in crude plant extracts is described. Antisera of high affinity and titer were obtained by immunizing rabbits with a conjugate of carboxyl-coupled GA3 and bovine serum albumin. [(125)I]Gibberellic acid-[N-(p-hydroxybenzyl) putrescine]amide of high specific activity, used as the immunotracer, is readily displaced by gibberellic acid methyl ester but not by free gibberellic acid. Thus, methylation of extracts prior to analysis is required. The assay is very specific; besides GA3, only the closely related GA7 is highly immunoreactive. Various gibberellins, related compounds, as well as other classes of plant hormones do not interfere with the assay. Levels of immunoreactive gibberellins (GA3, GA7) in actively growing tissues, among them cell suspension cultures of 33 different species, were determined.

Radioimmunoassays for trans-zeatin and related cytokinins

Radioimmunoassays for the quantitation of trans-zeatin and related cytokinins have been developed. Antisera produced against bovine serum albumin conjugates of trans-zeatinriboside have a high affinity (Ka=2.4.10(-11) M) for zeatinriboside and for zeatin, but show a negligible cross reaction to isopentenyladenosine (0.1%) and cis-zeatinriboside (0.4%), only a slight cross reaction to dihydrozeatin (1.7%), and no cross reaction at all to other purines, such as adenosine and related, compounds, was observed. The assays are sensitive and measuring ranges extend from 0.06-30 pmol (0.02-10 ng) of zeatinriboside. This has been achieved by employing as tracers immunoreactive zeatin derivatives with high-specific activity, (tritiated zeatinriboside-dialcohol: 8.37.10(11) Bq mmol(-1) and zeatinribosyl-[(125)I]tyramine: ca. 1.9.10(13) Bq mmol(-1). The detection limit is 40 fmol (15pg) for the assay employing the tritiated tracer, and assay reproducibility is high (variation coefficients of triplicates less than 5%). Several hundred assays can be completed in one day, and, due to the high specificity of this assay, crude extracts may be used for analysis. The course of zeatin levels in developing fruits of Lycopersicon esculentum cv. Moneymaker is given.