From the latex of Synadenium grantii Hook F. (Euphorbiaceae) were isolated by chromatographic methods five diterpene 12,13-diesters of the tigliane-type parent alcohols 4-deoxyphorbol (la), 4,20-dideoxy-5u-hydroxyphorbol (2a) and 20-.deoxy-5u-hydroxyphorbol (3a) with isobutyric, tiglic and phenylacetic acid. Of these, 4-deoxyphorbol-13-(phenylacetate)-12-tiglate (if) turned out to be highly irritant on the mouse ear while the rest of the esters had rather low or no irritant activity; if was also assayed for tumor-promoting activity and proved to be almost inactive. TLCSpots were detected under UV light (254 mm) and made visible with vanillin/sulfuric acid (13).Downloaded by: NYU. Copyrighted material.

A simple and fast procedure was worked out to prepare from the commercially available seeds of Euphorbia lathyris L. substantial amounts of the polyfunctional tetracyclic diterpene ingenol (la). Ingenol-3,4:5,20-diacetonide (1d) was treated with five different bases at two different temperatures to achieve epimerization to 8-epiingenol. In any case unchanged 1 d was obtained. By reduction of ingenol-3,4: 5,20-diacetonide (1d) with sodium in ether/2-propanol (9 R)-9-deoxo-9-hydroxyingenol-3,4:5,20-diacetonide (2b) was obtained and converted to the corresponding 5,20-monoacetonide 2e. Reduction of ingenol-5,20-acetonide (le) with LiAlH4 in tetrahydrofuran furnished the epimeric (9 S)-9-deoxo-9-hydroxyingenol-5,20-acetonide (3c).The (9 R)-monoacetonide 2e was used to prepare the 3-tetradecanoate 2c of (9 R)-9-deoxo-9-hydroxyingenol (2a). From the (9 S)-monoacetonide 3 c four 3-esters [butyrate (3d), tetradecanoate (3e), eicosanoate (3f), benzoate (3g)] of (9S)-9-deoxo-9-hydroxyingenol (3 a) were synthesized. The 3,4 : 5,20-diacetonides of 2a and 3a, i.e. 2b/3b were used to provide the 9-hexadecanoates 2 f and 3j. The irritant activities of the 3-esters of the (9 S)-series depend strongly on the nature of the acyl group, thus furnishing, e. g. the moderately irritant tetradecanoate 3e [compared to corresponding 3-esters lb of ingenol (la)] as well as the highly active benzoate 3g of 3 a. The (9 R)-3-tetradecanoate 2c exhibits comparable activity as its (9 S)-analogue 3e. Thus, the spatial orientation (R or S) of the 9-hydroxy function plays a significant but not a crucial role for irritant activity. Both epimeric (9 R)/(9 S)-hexadecanoates 2f/3j were non-irritant.

An efficient rhodium-catalyzed synthesis of dihydro-3,1-benzoxazine derivatives has been accomplished from aniline-derived 1,3-amino alcohols and N-sulfonyl-1,2,3-triazole. The developed reaction demonstrates the new reactivity of azavinyl carbenes and allows access to diverse substituted dihydro-3,1-benzoxazines in good yields. Importantly, the reaction was readily extended to diols and could be used for selective protection of amino alcohols with N-sulfonyl-1,2,3-triazole as the protecting reagent.

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