Totalsynthese von (+)-D-Homo-19-nortestosteron

Total Synthesis of (+)-D-Homo-19-nortestosterone A novel total synthesis of (+)-D-homo-19-nortestosterone ( 2 ) is described starting from (4a S, 5S)-5-(t-butoxy)-4a-methyl-4, 4a, 5, 6, 7, 7-hexahydro-3 H-naphthalen-2-one ( 3 ) as a chiral building block for the rings C and D. The key step involves combining of the derived reactive one-carbon atom adducts 5 and 6 with the β-keto ester 16 , a synthon for the rings A and B, to give the Δ⁹-4, 5-secosteroid 21 . 21 was readily transformed to the title compound 2 by hydrogenation and subsequent ring closure. Hydrogenation of the derived 3, 5-dione 22 followed by base-catalyzed cyclization gave the 17a-t-butoxy compound 27 and the 9β, 10α-D-homosteroid 29 as by-product.     

Totalsynthese von Decarboxybetalainen durch photochemische Ringöffnung von 3-(4-Pyridyl)alanin

Total Synthesis of Decarboxybetalaines by Photochemical Ring Opening of 3-(4-Pyridyl)alanine A photochemical approach is presented for the total synthesis of the decarboxybetalaines, which were previously known from the mild decarboxylation of the natural plant colorants, the betalaines: Irradiation of rac-3-(4-pyridyl)alanine ( 1 ) yielded the rac-2-decarboxybetalamic-acid-imine ( 4 , 86%), presumably via a Dewar pyridine 2 , a cyclic aminal 3 and an electrocyclic ring opening. The imine-zwitterion 4 was treated with three amines, namely (S)-cyclodopa ( 6 ), (S)-proline ( 7 ), and indoline ( 8 ), to afford three decarboxybetalaines, namely (2S)-17-decarboxybetanidine ( 9 , red, 34%), (2S)-13-decarboxyindicaxanthine ( 10 , yellow, 56%), and rac-16-decarboxyindobetalaine ( 11 , orange, 78%), respectively. The structures of these coloring matters were confirmed by their electrophoretic behavior and their spectroscopic properties. 17-Decarboxybetanidine 9 was shown to be a ca. 1:1 mixture of two C(15)-epimers 9a and 9b , separable by chromatography. The configuration of 9a was determined as (2S, 15S) and that of 9b as (2S, 15R), by correlating their optical rotations with those of betanidine ( 12a ) and isobetanidine ( 12b ), respectively. The decarboxybetalaines 9 , 10 , and 11 did not show the double-bond isomerism at C(β), (Cγ) of the chromophore which had been found characteristic for the corresponding betalaines 12 , 13 , and 14 .