<i>N</i>-Alkylation of Secondary Amines with Esters and Lithium Alanate*

SummaryThe development of a labeling method for secondary amines with [2-11 C]acetone is described since the R 2 N-isopropyl moiety is present in many biologically active compounds. The influence of a variety of parameters (e.g. reagents, solvents, temperature, and time) on the reaction outcome is discussed. Under the optimal reaction conditions, [ 11 C]1-isopropyl-4-phenylpiperazine ([ 11 C]iPPP) was synthesized from [2-11 C]acetone and 1-phenylpiperazine in a decay-corrected radiochemical yield of 72%.

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“…1-Isopropyl-4-phenylpiperazine 21 was used as a reference compound for chromatography. THF was freshly distilled from LiAlH 4 before use.…”

Section: Methodsmentioning

confidence: 99%

Reductive N‐alkylation of secondary amines with [2‐¹¹C]acetone

Meij

Carruthers

Herscheid

et al. 2003

Labelled Comp Radiopharmac

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“…Dimethylamme (0.945 g), dissolved in THF (8 mL), was added to a suspension of LiAlH4 (0.235 g) in THF (50 mL) and allowed to stir at room temperature for 1 h. The amine-LiAlH4 product was cooled to 0 °C, and methyl 3/3-acetoxy-25,26,27-trinorlanost-8-en-24-oate (0.15 g) dissolved in THF (25 mL) was added. The mixture was stirred for 2 h at 0 °C and 1.5 h at room temperature (Khanna et al, 1975). Water-THF (1:1 v/v, 10 mL), 3 N NaOH solution (10 mL), and water (20 mL) were added successively to the suspension.…”

Section: Methodsmentioning

confidence: 99%

Azasterol inhibition of .DELTA.24-sterol methyltransferase in Saccharomyces cerevisiae

Oehlschlager¹,

Angus²,

Pierce³

et al. 1984

Biochemistry

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The inhibition of the delta 24-sterol methyltransferase (24-SMT) of Saccharomyces cerevisiae by side-chain azasterols is related to their nuclear skeleton and side chain nitrogen position. Inhibitory power [I50 (microM)] was found to be in the order of 25-azacholesterol hydrochloride salt (0.05) greater than 25-aza-24,25-dihydrozymosterol (0.08) greater than 25-azacholesterol approximately equal to 25-azacholestanol (0.14) greater than (20R)- and (20S)-22,25-diazacholesterol (0.18) greater than 24-azacholesterol (0.22) greater than 25-aza-24,25-dihydrolanosterol (1.14) greater than 23-azacholesterol (4.8). In the presence of azasterols, S. cerevisiae produces increased amounts of zymosterol, decreased amounts of ergosterol and ergostatetraenol, and the new metabolites cholesta-7,24-dienol, cholesta-5,7,24-trienol, and cholesta-5,7,22,24-tetraenol. Kinetic inhibition studies with partially purified 24-SMT and several azasterols suggest the azasterols act uncompetitively with respect to zymosterol and are competitive inhibitors with respect to S-adenosyl-L-methionine (SAM). These results are consistent with at least two kinetic mechanisms. One excludes competition of azasterol and zymosterol for the same site, whereas a second could involve a ping-pong mechanism in which 24-SMT is methylated by SAM and the methylated enzyme reacts with sterol substrate.

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“…It has long been recognised that the decomposition of excess LAH at the end of the reduction can play a significant role in the presence of products and by-products. The use of certain esters, such as ethyl acetate (EtOAc), can result in the alkylation of the amine [25][26][27]. For example, N-methyltryptamine derivatives (19) have been found to be converted to N-ethyl-N-methyltryptamines (20) by the addition of EtOAc during the LAH reaction of amide 18 (Fig.…”

Section: The Speeter and Anthony Routementioning

confidence: 99%