A highly diastereoselective synthesis of 4-octulose and 2-deoxy-4-octulose from a -fructose derivative

Bishydroxylation of methyl

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1 with osmium tetraoxide proceeded with extremed high diastereoselectivity to give only methyl

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2. Configurations of the new stereogenic centers (C-2,3) in 2 were determined by degradation of the C-5,6,7,8 fragment to the well-known methyl

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7. Transformation of 2 into the required

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10, was achieved by a methodology that implied, protection to 8, reduction of the ester group in 8 to a hydroxymethyl group in 9, and finally deprotection to the free

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10. On the other hand, epoxidation reaction on

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11 afforded only the corresponding 2,3-anhydro derivative 12 with configuration, as could be demonstrated by degradation to (S)-1,2,4-trimetoxybutane 16, which synthesis is reported herein.     

Synthesis and X-ray analysis of 1-((1S)-phenylethyl)-azetidine-(2R)-piperidinamide

The crystal and molecular structure of a new azetidine-2-carboxylic amide derivative is described. The structure was solved by direct methods and refined by least squares methods toR1=0.0393 for 4264 reflections (withI>2(I)) The structure consists of two independent molecules which are chemically the same with slight differences in geometry. Crystal data: C₁₇H₂₄N₂O, monoclinic, space groupP2₁,a=8.3782(4),b=20.0342(13),c=9.7769(8) Å, =109.687(6)°,V=1545.1(2)ų,Z=4.     

Synthesis of Enantiopure Primary Amines by Stereoselective Ring Opening of Chiral Octahydro-1,3-benzoxazines by Grignard and Organoaluminum Reagents

Chiral 1,3-perhydrobenzoxazines 1, 2, and 9-14, prepared by condensation of 8-(benzylamino)menthol with different aldehydes, react with alkylmagnesium bromides and trimethylaluminum leading to the open amino alcohols 3a-d, 4a-d, and 15-20 in excellent chemical yields and good to excellent diastereomeric excess. The sequential elimination of the menthol appendage by heating with P(2)O(5) and the benzyl group by hydrogenolysis lead to primary amines 7a-d, 8a-d, and 27-30 in excellent chemical yields and ee. The addition of the alkyl group from the Grignard derivatives and the methyl group from the trimethylaluminum occurs from opposite sides of the heterocycle, yielding the final primary amines with the same stereochemistry.     

Novel Cleavage of Propargylamines by Reaction with Organolithium Compounds

Treatment of secondary aliphatic 2-bromoallylamines with an excess of an organolithium compound led to saturated amines in which the organic group of the organolithium compound is incorporated at the alpha carbon. On the other hand, the successive reaction of the former amines with BuLi and t-BuLi between -80 degrees C and rt gave 1,3-diamines or hexahydropyrimidines depending on the reaction time. The formation of these unexpected products involves initial generation of lithium propargylamides, which subsequently undergo cleavage of the C propargylic-C acetylenic bond induced by the organolithium present in each case in the reaction medium. A mechanism which takes into account all the different reaction products has been proposed and additionally supported by successful trapping of dilithium acetylide.