A versatile synthetic route to pterosins, sesquiterpenoid indanones present in bracken, Pteridiumaquilinum, has been developed. The route is exemplified by the synthesis of (2S,3S)-pterosin C by Friedel–Crafts bisacylation of the methyl ether of 2-(2,6-dimethylphenyl)ethanol with methylmalonyl chloride. Demethylation of the resulting 1,3-indandione and reduction with zinc and acetic acid in the presence of acetic anhydride and sodium acetate afforded a mixture of racemic cis and trans isomers of pterosin C diacetate, which was hydrolysed to the corresponding pterosins. Separation and resolution via the S-(+)-α-phenylbutyric esters gave (2S,3S)-pterosin C and (2R,3R)-pterosin C. Other pterosins were prepared as racemates from the 1,3-indandione.

The synthesis of tritiated maleactivating steroids of the aquatic fungus Achlya, 7deoxy-7dihydroantheridiol (7DA) and antheridiol, has been achieved by aldol condensation of 3pacetoxy-23,24dinorchola-l ,Sdien-224 and the carbanion of 3isopropyl-2-butenolide. The product with the desired stereochemistry (22SJ3R) was isolated and reduced with 'Ha in the presence of tris(tripheny1phosphine)rhodium chloride. Acid hydrolysis of the acetate gave lJ['H]-7DA which had a specific activity of 40 Ci/mmol. lJ['H]-7DA was converted to 1,2[3H]-antheridiol by protecting the hydroxyl groups as the disilyl ethers, oxidation to the 7ketone with chromium trioxidedimethylpyrazole and removal of the protecting groups by gentle acid treatment. 1,2['H]-7DA has been used to detect a protein receptor in the cytosol of Achlya.There is little information on the effects of steroid binding on the receptor molecule, how the receptor complex moves to nuclear sites, or what the receptor complex does at nuclear sites to alter gene expression.An attractive organism for studying such questions is the primitive eukaryote Achlya ( 1 ) . Female strains of this fungus, eg A. ambisexualis 734, secrete the steroid antheridiol (1) which acts on male strains, eg A . ambisexualis E87, inducing differentiation of sexual hyphae (antheridial branches).Antheridiol also induces the production of further sex steroids, oogoniol(2) and dehydrooogoniol (3) by the male. The latter steroids cause sexual differentiation in the female leading to formation of the oogonium (2).The hyphae of A . ambisexualis E87 are extremely sensitive to antheridiol and under suitable conditions will respond to concentrations of antheridiol as low as 6 picograms/mL (10-"M) within two hours.Developmental responses include an early stimulation of RNA and protein synthesis within the first few hours. Inhibitor studies show that the morphological changes depend upon RNA and protein synthesis (3.4). These results are not unlike those obtained for steroid hormone action in higher organisms. Therefore, although Achlya cells differ greatly from cells in the rat uterus or chick oviduct, it is tempting to speculate that the basic mechanism of steroid hormone action in these target cells may be quite similar.In this paper we report on our efforts to synthesize tritium4abelled antheridiol with a specific activity sufficient to initiate studies on the binding and fate of the hormone in target cells.Several approaches were studied and are summarized as follows:A. The most expedient method for obtaining a tritiated compound was to synthesize antheridiol-3acetate using [3H]-acetic anhydride.' This was prepared with a specific activity of about 3 Ci/mmol. Antheridiol acetate is biologically active, but it is not known whether the acetate remains intact within the organism. Initial attempts to observe specific binding of this compound to Achlya were unsuccessful. B. We investigated ways of introducing the label into ring C of the steroid. Specifically, a derivative containing an 11,12 double bond was prep...