Selective hydrolysis of .alpha.,.beta.- and .beta.,.gamma.-unsaturated ketals: method for deconjugation of .beta.,.beta.-disubstituted .alpha.,.beta.-unsaturated ketones

Concise Synthesis of Yashabushidiol A and (±)‐Diospongin A

“…Finally, the debenzylidenation 13 and desulfurization 14 were achieved in 74% and 64% yields, respectively. The key transformation was the treament of 6 with Me 3 SiOTf, then Et 3 SiH, in a salt-ice bath for 15 minutes, thereby affording the target molecule (±)-diospongin A in 42% yield.…”

“…11,12 The optimal conditions we found involves tosylation of 1 in pyridine at 0 o C for 12 h, but a yield of only 36% was obtained. The next step was protection 13 of the free hydroxyl groups in the form of a 2-phenyl-1,3-dioxane derivative. While benzylidenation with benzaldehyde was inefficient, transacetalization with benzaldehyde dimethyl acetal proved satisfactory, 3 was produced in 77% yield.…”

“…It is evident that intermediates 4, 5, and 7 can be readily converted into yashabushidiol A (8). We arbitrarily chose 7 to complete the conversion and found the combined debenzylidenation and reduction 13 proceed better with the Pd(OH) 2 /C catalyst than the more common Pd/C; yashabushidiol A was obtained in 72% yield.…”

“…2H, br);13 C NMR: d = 200.1, 136.7, 133.6, 128.69, 128.11, 68.1, 45.3, 41.9. HRMS (ESI): m/z (M+Na + ) calcd for C 19 H 24 O 4 : 335.1254; found: 335.1257.…”

Towards NO‐free Regulation of sGC: Design and Synthesis of trans‐AB‐porphyrins

“…We speculated that the dipyrromethane forming reaction failed because the acetal 14 was not deprotected. Therefore, it was first hydrolyzed to the respective aldehyde 15 and then reacted with an excess of pyrrole (Scheme ) 23c. In this case, the reaction afforded dipyrromethane 16 in 42 % yield.…”