The male antifertility activity of 6-chloro-6-deoxyglucose

Lack of antifertility properties of novel halogenated glycolytic inhibitors and the urinary excretion and metabolism of 1,6-dichloro-1,6-dideoxy-D-fructofuranose in the male rat

The antifertility action of (R,S)-alpha-chlorohydrin administered orally to male rats was compared with that of several novel chlorinated compounds known to inhibit glycolysis and the kinematics of rat sperm in vitro. Oral gavage of 1,6-dichloro-1,6-dideoxy-D-fructofuranose (dichlorodideoxyfructose, DCF), 1-chloro-3-hydroxypropanone, its dimethylketal and bromopyruvate did not reduce the fertility of male rats below that of controls at the equivalent antifertility dose of (R,S)-alpha-chlorohydrin (5 mg/kg/day) or higher. As anticipated for a compound cleaved to products of (S)-chirality even high doses of DCF (200 mg/kg) showed no effect on renal function. 36Cl-Labelled DCF administered orally to male rats was eliminated only slowly in the urine (16% of the ingested dose excreted in 96 h). In the first 8 h, approximately 50% of DCF was excreted unchanged, 30% was excreted as 3-chlorolactate (BCLA), the oxidation product 3-chlorolactaldehyde and 25% as Cl-. By 24 h little DCF remained and the major metabolite (70%) was BCLA and 20% Cl-. The high rate of dechlorination is most likely responsible for the low antifertility action of DCF.

A re-appraisal of the post-testicular action and toxicity of chlorinated antifertility compounds

Some 30 years ago, alpha-chlorohydrin and some analogues were considered as close to the ideal contraceptive which acted rapidly and reversibly on the post-testicular maturation of spermatozoa. Despite their early promise, research funding was withdrawn only 5 years later because of what were considered to be unacceptable side-effects in primates. The literature on the toxic effects of these contraceptive agents was reviewed and was found to be wanting in respect to the rigour of scientific methods applied (impure compounds were used, inappropriate target populations were studied, excessive doses were employed, abstracts were cited from which no full publications subsequently arose). These compounds remain the closest approach yet to non-hormonal contraceptives for males and have led to the synthesis of related compounds which have a similar antifertility action but with much diminished toxicity. If toxicity remains a problem, a range of other compounds now known to have a similar antifertility action, should be investigated.

Inhibition of glycolysis in boar spermatozoa by 1,6-dichloro-1,6-dideoxy-D-fructose

The dichloro-analogue of D-fructose 1,6-bisphosphate, 1,6-dichloro-1,6-dideoxy-D-fructose, is a weak substrate for boar sperm aldolase which converts it to (S)-3-chlorolactaldehyde and 3-chloro-1-hydroxypropanone in vitro. Production of these chloro-trioses leads to the strong inhibition of glyceraldehyde-3-phosphate dehydrogenase, the weak inhibition of triosephosphate isomerase and the transient inhibition of aldolase.