Furfurylidene group

An example is the preparation of 18-trideuterio 5a-steroids bearing a side chain at C-17. Labeling of this position with three deuteriums was accomplished by utilizing the Johnson procedure for steroid total synthesis. This synthesis involves, in part, introduction of the 18-angular methyl group by methylation of the D-homo-17a-keto-17-furfurylidene intermediate (243). By substituting d3-methyl iodide in this step, the C/D cis- and ra/J5-18,18,18-d3 labeled ketones [(244) and (245)] are obtained. Conversion of the C/D tra 5-methylation product (245) into 18,18,18-d3-d /-3)8-hydroxy-5a-androstan-17-one (246) provides an intermediate which can be converted into a wide variety of C-18 labeled compounds of high (98%) isotopic... 

Acetals are readily formed with alcohols and cyclic acetals with 1,2 and 1,3-diols (19). Furfural reacts with poly(vinyl alcohol) under acid catalysis to effect acetalization of the hydroxyl groups (20,21). Reaction with acetic anhydride under appropriate conditions gives the acylal, furfurylidene diacetate [613-75-2] (22,23). 

Its derivative with a further furfurylidene substituent on its methyl group (270 daltons) was not found to be present. 

The experimental evalution of acute toxicity of germyl(silyl)-substituted furfurylidene Meldrum acid (Table 5) has demonstrated that the introduction of the trimethylgermyl group lowers the toxicity of the compound by ca 4 times. On the other hand, the introduction of the trimethysilyl group does not change significantly the toxicity of the unsubstituted derivative. The carbon analogue is the most toxic derivative in this series of compounds . 

Poly(hydroxymethyl furfurylidene-acetone) adhesive resins were synthesized and characterized [68-70] through the 5-formaldehyde adduct (19) and its acid-catalyzed polymerization. The catalysts used were sulfuric, phosphoric, or p-toluenesulfonic acid. The authors postulated that the first condensation products resulted from the condensation of two methylol groups of two 19 molecules (adduct 20). They also proposed a hypothetical structure of the network formed after curing (21). It seems, however, difficult to envisage the acid-catalyzed resinification of 19 without the participation of hydrogen atoms at the C5 position of the furanic ring [2]. 

The application to the trans-A/B hydroxyketone (158) of the usual sequence of reactions of angular methylation and the contraction of ring D permitted the preparation of dZ-epiandrosterone (175) and its ISa- ("lumi-") epimer (174) [356] (Scheme 97). In the furfurylidene derivative (166) obtained from (158), the 3/3 -hydroxy group was protected in the form of the tetrahydropyranyl ether and after angular methylation and hydrolysis the cis-C/D isomer (168) and trans-C/D isomer (169) were obtained in a ratio of 2.2 1. The trans-C/D-isomer (169) was acetylated by an exchange re-... 

On angular methylation with protection of the 3o -hydroxy group in the form of the tetrahydropyranyl ether, the furfurylidene derivative (180) formed the trans-C/D and the cis-C/D methyl derivatives (177) and (181), respectively, in a ratio of 1 3.8. Transacetylation, ozonolysis, and esterification of the trans-methyl derivative (177) led to the diester (178), the Dieckmann reaction of which followed by acid hydrolysis gave the hydroxy ketone (179). Oxidation of the 30 -hydroxy group of the latter and the introduction of a A -bond by bromination and dehydrobromination led to the yeast Saccharomyces cerevisiae by a known method [927], a mixture of the c -enantiomer of testosterone (182) and the Z-enantiomer of androstene-dione (183), which were separated chromatographically, was obtained with yields of 70 and 73%, respectively. The over-all yield of Z-testosterone (182) in this synthesis amounted to 2.9% on the (162) (twelve stages) and 1.1% on the unsaturated ketone (140) (16 stages) [921]. 

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