Formation of 1-phenyl-2,3-dioxabicyclo[2.2.1]heptane in the reaction of 1,3-dibromo-4-phenylcyclopentane with hydrogen peroxide in the presence of silver trifluoroacetate
Synthesis of the Ribosomal P-Site Substrate CCA-pcb
摘要:
CCA-pcb (cytidylyl-(3'5')-cytidylyl-(3'5')-3'(2')-O-(N-(6-D-(+)-biotinoylaminohexanoyl)-L-phenylalanyl)adenosine), a ribosomal P-site substrate, was synthesized by phosphoramidite chemistry in 26 steps with an overall yield of 18%, starting from biotin. The synthesis relies on the judicious selection of orthogonal silyl protecting groups for the 5'-hydroxyls and acid-labile protecting groups (DMTr, AcE, and MeE) at other reactive sites to ensure the intactness of the labile ester. Both X-esterification and nucleotide coupling were accomplished by in situ activation with imidazolium ions.
Biologically active quassinoids : synthetic methodology for the conversion of chaparrin into glaucarubolone esters and quassinoid analogs
作者:Subodh C. Bhatnagar、Andrew J. Caruso、Judith Polonsky、Berta Soto Rodriguez
DOI:10.1016/s0040-4020(01)81638-0
日期:1987.1
Biologically inactive but easily available chaparrin has been converted into potent antileukemic C-15 esters of glaucarubolone and quassinoid analogs in which the C-15 ester side chain has been replaced by an alkyl or alkenyl group.The synthetic methodology developed has been applied to the preparation of C-15 ester derivatives , , and quassinoid analogs , and .
The title compounds, (+)-13-methyl-13-dihydro-4-demethoxydaunorubicin hydrochloride (8·HCl) and (+)-13-methyl-13-dihydrodaunorubicin hydrochloride (9·HCl), were prepared from (+)-4-demethoxydaunomycinone (13) and (+)-daunomycinone (18), respectively, by silylation of the C7-hydroxy group, addition of methylmagnesium bromide to the C13-carbonyl group, and direct glycosidation of the 7-O-silyl anthracyclinones with the daunosamine derivative (anthracycline numbering). In the P388 in vitro test, 8·HCl was several hundred-fold more active than adriamycin hydrochloride (1·HCl). Notable anticancer activity, equivalent to that of adriamycin hydrochloride, was also observed in the P388 in vivo test of 8·HCl.
construction of quaternary centers with a trifluoromethyl group was realized by way of 1,6-addition of various nucleophiles including active methylene compounds to highly reactive δ-trifluoromethylated p-quinone methides generated in situ from the corresponding tertiary carbonates with a catalytic amount of an appropriate base.
Boron Compounds; 69<sup>1</sup>. Introduction and Removal of<i>t</i>-Butyldimethylsilyl Groups via Diethylboryloxy Compounds
作者:Wilhelm V. Dahlhoff、Kalulu M. Taba
DOI:10.1055/s-1986-31703
日期:——
O-Diethylboryl compounds react with t-butyldimethylsilylacetylacetonate in the presence of trimethylsilyl triflate at room temperature to give the corresponding t-butyldimethylsilyl ethers, which are easily deprotected, forming O-diethylboryl ethers on reaction with tetraethyldiboroxane.