Zur Prins‐Reaktion von Lumihecogeninacetat

Abstract

Durch photochemische Umlagerung von Hecogeninacetat (1) zum ungesättigten Aldehyd 5 und anschließende Prins‐Reaktion sind die 14β‐Hydroxysteroide 7a und 10a bequem zugänglich. Die Konfiguration an C‐13 und C‐14 bei 7a, 10a und 9a wurde chemisch und mit Hilfe spektroskopischer Methoden (1H‐NMR, 13C‐NMR und CD) abgeleitet.

A Novel Oxidative Cleavage of the Steroidal Skeleton

“…On treating the D 14, 15 -double bond in steroids of the hecogenine series with MCPBA Welzel and co-workers obtained, in contrast to other steroidal classes, mainly the 14,15b-epoxide. [16] Our own investigations confirmed the general b-diastereoselectivity of the epoxidation observed by Welzel et al in the hecogenine series, when we treated homoallylic alcohol 3 and its corresponding 12-acetate 13 [16] with MCPBA (Scheme 3). These results clearly demonstrate that the compound obtained by Bladon and co-workers [9] on MCPBA-epoxidation of 3 is definitely the 14b,15b-epoxide 14, and not the originally proposed 14a,15a-epoxide.…”

“…These results clearly demonstrate that the compound obtained by Bladon and co-workers [9] on MCPBA-epoxidation of 3 is definitely the 14b,15b-epoxide 14, and not the originally proposed 14a,15a-epoxide. This outcome is also indirectly indicated from the configurational proof of the (25 R)-3b-acetoxy-5a,14b-spirostan-12a,14-diol reported by Welzel et al [16] The characteristic structural element of bisketal 12 is the 4-hydroxy-[2.2.2]-1,3-dioxabicylooctane unit 16 (Scheme 4). This substructure is also present in the natural diterpene ponicidin 17 [24] and in several synthetic compounds, [25] prepared by other methods.…”

“…Although various synthetic studies on the D 14,15 -double bond of homoallylic alcohol 3 and its derivatives have been described, [9,15,16] it is interesting that there are no reports on a syn-dihydroxylation. Therefore, we were not surprised when no reaction occurred on treatment of homoallylic alcohol 3 under the standard osmium tetroxide ± dihydroxylation conditions.…”

“…In this case lactol 22 or lactone 23 were potential cyclization products of the oxidative fission (Scheme 5). The 12b-homoallylic alcohol 19, readily available by PCC-oxidation [16] and subsequent diastereoselective reduction [8] of its 12a-epimer 3, was treated with ruthenium trichloride/sodium periodate to provide only the 12b-14/15b-glycol 20 in moderate yield with no ring-opened material being observed (Scheme 5).…”

Eigenschaften eines (Arylthiomethylen)cyclohexanons

“…Auch bei Aufnahrne der 'H-NMR-Spektren in Gegenwart von Eu(fod)3 ergaben sich analoge Befunde wie bei l a und l b . - ( ( 3-/4-Chlorphenylthio)-7,7-dimethyl-2-phenyl-4,5,6,7-tetrahydrobenzofuran (9 (100); 286 (17), 143 (32); 108 (17). (10); 251 (28); 151 (85); 123 (100).…”