- Enantioselective synthesis of ethyl 4,5,7,8,9-penta-O-acetyl-2,6- anhydro-3-deoxy-D-erythro-L-gluca-nononate: A 2-monodeoxygenated derivative of '2-keto-3-deoxy-D-glycero-D-galacto-nononic acid'
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A study aimed at developing an enantioselective synthesis of the title compound 23, a 2-monodeoxy analogue of the naturally occurring (+)-2-keto-3- deoxy-D-glycero-D-galacto-2-nononic acid (KDN), is reported. From D-mannose as starting material, the chiral 1,3-diene 10, activated by a silyloxy substituent at C(2), was prepared in six steps (Scheme 1). However, the intermediates were often contaminated with varying amounts of by-products arising from overoxidation during cleavage with periodic acid. An alternative route starting from the inexpensive and readily available D-isoascorbic acid (12), though a little longer than the first, satisfactorily circumvented the purification problem and led to the desired dienes 17 in good yields (scheme 2). The [Co11(S,S)-(+)-salen]-catalyzed hetero-Diels-Alder reactions of the aforementioned dienes with ethyl glyoxylate proceeded smoothly at room temperature, giving the dihydropyrano adducts 18 in moderate yields (Scheme 3). Dihydroxylation of 18a followed by reduction of the keto function gave the desired 4,5-trans dihydroxy moiety of the KDN framework (Scheme 4, see 21). The spectroscopic data of the penta-O-acetylated 2-deoxy-KDN ethyl ester 23 were consistent with those reported for the corresponding methyl ester derived from natural KDN.
- Shen, Xin,Wu, Yu-Lin,Wu, Yikang
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p. 943 - 953
(2007/10/03)
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- Highly stereocontrolled access to a tetrahydroxy long chain base using anti-selective additions
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Complete diastereostereoselection was attained for the addition of acetylide and benzyloxymethyl anions to a chiral aldehyde and an imine derived from meso-tartaric acid, leading to a facile synthesis of (2S,3S,4R,5R,6Z)-2-amino-1,3,4,5-tetrahydroxyoctadecene as its pentaacetyl derivative in enantiomerically pure form.
- Shimizu, Makoto,Kawamoto, Manabu,Niwa, Yasuki
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p. 1151 - 1152
(2007/10/03)
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- Reductive Cleavage Reaction of γ-Functionalized α,β-Unsaturated Esters and Halomethyls Mediated with Magnesium in Methanol
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Reductive cleavage of various types of C-O and C-N bonds tethered to α,β-unsaturated esters and halomethyls was mediated with magnesium in methanol, which provided a facile method for the synthesis of δ-hydroxy or δ-amino β,γ-unsaturated esters and allylic alcohols.Regardless of the geometry (E or Z) of the α,β-unsaturated esters, 1a-b, 5a-c, 11, 13, and 23, the cleavage product obtained was exclusively the E isomer of the corresponding deconjugated hydroxy and amino esters.The steric bias and ring strain of 15, 17, and 21 gave rise to a product mixture of E and Z isomers.
- Pak, Chwang Siek,Lee, Eun,Lee, Ge Hyeong
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p. 1523 - 1530
(2007/10/02)
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- 4-O-benzyl-2,3-O-isopropylidene-D-erythrose and -D-threose from 2,3-O-isopropylidene-D-glyceraldehyde via thiazole intermediates. Synthesis of 2-deoxykanosamine
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The adduct derived from 2,3-O-isopropylidene-D-glyceraldehyde and 2-(trimethylsilyl)thiazole is readily converted into the title D-erythrose (50% overal yield) by selective protection of the hydroxy groups and cleavage of the thiazole ring; the D-threose
- Dondoni,Merino
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p. 196 - 200
(2007/10/02)
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- Synthesis of Saccharides and Related Polyhydroxylated Natural Products. 1. Simple Alditols
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A new approach to sugar synthesis is demonstrated through syntheses of tetritols, pentitols, and hexitols; titanium-catalyzed asymmetric epoxidation and a new selective opening reaction of 2,3-epoxy alcohols play essential roles.
- Katsuki, T.,Lee, A. W. M.,Ma, P.,Martin, V. S.,Masamune, S.,et al.
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p. 1373 - 1378
(2007/10/02)
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