The amplitude of acoustic startle is markedly enhanced by cues signaling moderately intense footshocks but, surprisingly, not by cues signaling higher intensity footshocks. Previous findings suggest that the ineffectiveness of high footshock training may involve activation of the dorsal periaqueductal gray (PAG). As a means of evaluating this possibility, rats trained with moderate (0.6 mA) footshocks were later tested after intra-PAG infusion of an excitatory nontoxic dose of kainic acid. Kainic acid significantly reduced fear-potentiated startle relative to vehicle controls. In a 2nd experiment, the effect of dorsal PAG lesions on fear-potentiated startle to cues paired with 0.6-mA and 1.6-mA footshocks was evaluated. Dorsal PAG lesions prevented the disruptive effects of high footshock training. Together, these results suggest that dorsal PAG activation mediates the loss of potentiated startle accompanying high footshock training.

Alcohols possessing an α-hydrogen, acetals, and aldehydes undergo photochemically induced conjugate addition to a variety of α-enones to give 1,4-ketols, 1,4-keto ketols and 1,4-diketones respectively. It appears that the aldehydes frequently succeed where acetals and alcohols fail, and acetals where alcohols fail. It is therefore possible to employ polyfunctional addenda and achieve addition at only one of the activated sites. The reactions are always regiospecific and are frequently completely stereoselective.

. The photochemically induced conjugate addition of simple alcohols to a variety of a-enones has been investigated. With hex-2-enopyranosid-4-uloses (I), the alkylations occur from the less-hindered side and are completely stereo-and regioselective. The resulting 1,4-ketoalcohols (2) are readily cyclized to a-cyclopropyl ketones which have been prepared by alternative, less desirable routes. Alkylative additions of hex-1-enopyran-3-uloses occur also although less readily and without stereospecificity, giving C-glycosides. 2-Cyclohexenone and carvone are also photoalkylated by methanol giving moderate yields of the 1,4-ketols. In the case of carvone, carvone camphor was not detected as a by-product. Steroidal a-enones and mesityl oxide both fail to be photoalkylated by methanol. BERT FRASER-REID, NEVILLE LEWIS HOLDER, DAVID ROY HICKS et DAVID LOUIS WALKER.Can. J. Chem. 55,3978 (1977).L'addition conjuguee photochimiquement induite d'alcools simples a une variete d'knones-a est ttudiee. L'alkylation des hexeno-2 pyrannosiduloses-4 (1) a lieu sur le cBtC le moins encombre de la molkcule et est compl&tement stereo et rCgiosClective. Les c6toalcools-l,4 (2) resultants sont ensuite cyclises en a-cyclopropyl cttones lesquelles ont tte preparees par des routes moins desirables. L'addition par alkylation des hextno-l pyrannuloses-3 se produit aussi quoique moins facilement et sans stereospecificitk, conduisant B des C-glycosides. La cyclohexkne one-2 et la carvone sont aussi photoalkylCes par le methanol conduisant avec un rendement moyen aux cetols-1,4. Dans le cas de la carvone, la carvone-camphre n'est pas dttectte comme produit secondaire. Les Cnones-a dans la sCrie des stCroldes ainsi que I'oxyde de mksityle ne sont pas photoalkylts par le methanol.[Traduit par le journal]The ready availability in recent years of carbohydrate a-enones (1) has prompted the use of these versatile compounds in a variety of syntheses (see for example ref. 2). Conjugate-addition-alkylation of these enones offers simple access to biologically important branched-chain sugars, and hence we undertook an examination of a number of such reactions (3). In an accompanying paper (4) we report our results on the stereochemical course of copper-induced additerebic acid, Schenck et al. added isopropanol to maleic acid (6). The reaction has been of interest to photochemists (7) but prior to our own work (3) there was only oile recorded investigation of its synthetic utility (8), and the results therefrom were not encouraging. In this and the accompanying paper (5), it will be shown that the photoalkylation reaction is a simple and highly promising method of carbon-carbon bond formation. Experiments to determine some mechtion of organometallic reagents to some carbo-anistic as~ects of these reactions are currently hydrate enines. In this an; the following paper underwaGand will be reported in the future.---(5) we describe the photoinduced addition of oxycarbinyl species to these enone receptors.Additions to Alkyl Hex-2-enopyranosid-4-The photoinduced a...

Whereas the pseudo-axial 3-hydroxyl group of allal derivatives is known to be inert to manganese dioxide oxidation, the equatorial counterpart in glucal derivatives is shown to be readily oxidized. Thus glucal is converted to the 6-O-triphenylmethyl ether or 6-O-benzoyl ester to promote solubility in chloroform, and the derivatives are oxidized in that solvent in 12 h or less.Acetonation of glucal is readily accomplished in 45 min using 2,2-dimethoxypropane and p-toluenesulfonic acid in dimethylformamide; the product may be oxidized directly either with manganese dioxide or dipyridine chromium oxide. Thus it is possible to obtain 1–3-g quantities of the crystalline acetonated enone from triacetyl glucal (via deacetylation, acetonation, and oxidation) in 3–4 h.If the acetonation medium stands for 2 h methyl 2,3-dideoxy-4,6-O-isopropylidene-α-D-erythro-hex-2-enopyranoside is obtained. The mechanism of its formation in the reaction medium is discussed.

The chemical stability of oligonucleotides (ODNs) containing 3'-propanolamine was investigated. Invariably, all the ODNs synthesized from Fmoc-protected 3-aminopropane-1,2-diol-CPG support gave a mixture of three compounds at the end of automated synthesis as analyzed by denaturing PAGE and HPLC. On the basis of analytical procedures, these compounds were identified to be 3'-[N-acetyl-N-(hydroxypropyl)amino],3'-[(hydroxypropyl)amino], and 3'-hydroxyl ODNs. The instability of the amino protecting group under the synthesis conditions was responsible for this observed heterogeneity. In order to evaluate the stability, a comparative study on the chemical stability of the ODN containing amino-protecting groups such as [(9-fluorenylmethyl)oxy]carbonyl (Fmoc), trifluoroacetyl (TFA), and phthaloyl was undertaken. The results indicate that the phthaloyl group provided the best stability for the synthesis of 3' amine-modified ODNs, and the protecting group is cleaved and deprotected in concentrated ammonium hydroxide:40% aqueous methylamine, 1:1, for 5-10 min, at 56 degrees C. The 3'-hydroxypropyl)triglycyl] ODN conjugates were also synthesized from Fmoc- and phthaloyl-protected (hydroxypropyl)triglycine-CPG supports.