Convergent synthesis of (2R,3R,8R,9R)-N-Boc-ADDA

The convergent synthesis of N-Boc-(2R,3R,8R,9R,4E,6E)-3-amino-9-methoxy-2,6,8-trimethyl-10-phenyldecadenoic acid (enantio-N-Boc-ADDA) is reported. Our flexible approach takes advantage of highly efficient non-aldol aldol and cross-metathesis methodologies.     

Novel,short, stereospecific synthesis of lyxo-(2R,3R,4R)-phytosphingosine and erythro-(2R,3S)-sphingosine

Lyxo-phytosphingosine and erythro-sphingosine have been elaborated from a common intermediate. The key step in the reaction sequence involves stereo- and regiospecific functionalization of an olefin by intramolecular nucleophilic sulfinyl group participation.     

Chiron approach to the synthesis of (2S,3R)-3-hydroxypipecolic acid and (2R,3R)-3-hydroxy-2-hydroxymethylpiperidine from D-glucose

The first chiron approach from d-glucose for the total synthesis of (2 S,3 R)-3-hydroxypipecolic acid (-)-1a and (2R,3R)-3-hydroxy-2-hydroxymethylpiperidine (-)-2a is reported. The synthetic pathway involves conversion of d-glucose into 3-azidopentodialdose (5) followed by the Wittig olefination and reduction to give the piperidine ring skeleton (8) with a sugar appendage that on cleavage of an anomeric carbon followed by oxidation gives (-)-1a which on reduction affords (-)-2a.     

Studies on the transformation of nitrosugars into iminosugars III: synthesis of (2R,3R,4R,5R,6R)-2-(hydroxymethyl)azepane-3,4,5,6-tetraol and (2R,3R,4R,5R,6S)-2-(hydroxymethyl)azepane-3,4,5,6-tetraol

A divergent synthesis of the two novel polyhydroxylated azepanes (2R,3R,4R,5R,6R)-2-(hydroxymethyl)azepane-3,4,5,6-tetraol and (2R,3R,4R,5R,6S)-2-(hydroxymethyl)azepane-3,4,5,6-tetraol from d-mannose is described. The method involves a Henry reaction between dimethyl-tert-butylsilyl 2,3-O-isopropylidene-α-d-lyxo-pentodialdo-1,4-furanoside and 2-nitroethanol followed by a reductive ring closure of the resulting epimeric nitro aldols. Glycosidase inhibition tests showed that (2R,3R,4R,5R,6S)-2-(hydroxymethyl)azepane-3,4,5,6-tetraol exhibits a weak but selective inhibition against α-l-fucosides.     

Preparation of (2R, 3R, 4R)-3-hydroxy-2,4,6-trimethylheptanoic acid via enzymatic desymmertization

Synthesis of a unique fatty acyl unit to build the N-terminus of callipeltin A and homophymine B is described. Our approach to access (2R, 3R, 4R)-3-hydroxy-2,4,6-trimethylheptanoic acid uses enzymatic hydrolysis for the desymmetrization of achiral acetate, followed by diastereoselective Roush crotylboration and Wittig olefination for the backbone construction.     

"一锅法"合成N-链烯基-(2R,3R)-O,O-二乙酰酒石酰亚胺

本文报导一种由(2R,3R)-二乙酰酒石酸酐合成N-ω-链烯基二乙酰酒石酰亚胺的简单有效的"一锅合成法", 并使总产率有大幅度的提高。     

A New Compound with C_2-Symmetry 3R,3''''R-Dihydroxy-6,6'''',6,6''''-tetramethyl-2R,2''''R,-bis-4H-pyran

InthepasttWentyyearsalargenumberofC2-syInInetryligandshavebeenreportedaschiralauxiliariesinasyInInetricsynthesis,amongwhichsomebiarylsethibitexcellentchthelselectivity."lnthispaPerwewouldreportthesynthesisofanewC2-smpetrycomPOundl,whichhastwopyranringsinsteadoftWoaromaticringsofbinyls.l,2,5-6-Diapydro-3,4-isopropylideneD-mannitol2,whichwaspreparedfromD-mannitolbyknownprocedure',wasusedasthestartingmaterialinthissynthesis.Thecarbonchainaibothterminalsofcompound2wasextendedb}'treatmentof2wi…     

Dialkylindiumacetate R2InOOCCH3 (R = CH3, C2H5) Darstellung,Eigenschaften und Struktur

Dialkylindium Acetates R₂InOOCCH₃ (R = CH₃, C₂H₅). Preparation, Properties, and Structure. Dimethyl- and diethylindium acetate were prepared and the vibrational spectra (IR and RAMAN ) discussed. The X-ray structure determination shows that diethylindium acetate belongs to the orthorhombic space group Pnma. The unit cell with lattice constants a = 8.40, b = 7.41, c = 15.13 Å contains four molecules. Each indium atom forms with an acetate group a planar four-membered ring. The indium-oxygen distance within such a ring is only a little shorter than the distance of this oxygen to the indium of the next neighboured ring. Indium has therefore the coordination number six.     

Novel,efficient and stereospecific synthesis of xylo-(2R,3S,4S)-phytosphingosine and threo-(2R,3R)-sphingosine

The stereo- and regioselective elaboration of a bromohydrin from an olefinic precursor and Pummerer ene reaction for carboncarbon bond formation are the key steps in a novel and flexible synthesis of xylo-phytosphingosine and threo-sphingosine.     

Synthesis of (+)-2R,3R,11R,12R- and (−)-2S,3S,11S,12S-tetraphenyl-18-crown-6

The synthesis of the title crown ethers starting from optically active hydrobenzoins is described. R(+)-1,in CDCl₃ ,preferentially extracts R(+)-phenylglycine methyl ester hydroperchlorate from an aqueous solution of the racemate with a chiral recognition factor of 1.5 as shown by nmr measurements.     

Synthesis of 2S-Hydroxymethyl-3R, 4R-dihydroxypyrrolidine

Manyp0lyhydroxylatedalkaIoidsexhibitglyc0sidaseinhibit0ryactivitiesl.PoIyhyroxylatedpyrroIidineisatypeofimportantalkaloidalglycosidaseinhibit0rs2.Forexample,2R-hydroxymethyl-3R,4R-dihydroxypyrr0lidine(l,4~dideoxy-1,4imin0-D-arabinitoI),anaturallyoccurringp0lyhydroxylatedpyrrolidine',isapotentinhibitorofa-glucosidase'.Promptedbyinterestsintheremarkablephysi0logicaleffects,s0mepolyhydroxylatedpyrrolidineandtheirderivativeshavebeensynthesized".Inthispaper,wedescribethesynthesis0f2Shydroxymeth…     

Asymmetric synthesis of (2S,3R,4R)-ethoxycarbonylcyclopropyl phosphonoglycine

The synthesis of enantiomerically pure (2S,3R,4R)-ethoxycarbonylcyclopropyl phosphonoglycine is described, the key-step involving 1,4-addition of a chiral enolate to ethyl 4-bromo-crotonate.     

Über den Phosphandiyl‐Transfer von invers‐polarisierten Phosphaalkenen R1P=C(NMe2)2 (R1 = tBu,Cy, Ph,H) auf Phospheniumkomplexe [(η5‐C5H5)(CO)2M=P(R2)R3] (R2 = R3 = Ph; R2 = tBu,R3 = H; R2 = Ph,R3 = N(SiMe3)2)

Phosphanediyl Transfer from Inversely Polarized Phosphaalkenes R¹P=C(NMe₂)₂ (R¹ = tBu, Cy, Ph, H) onto Phosphenium Complexes [(η⁵‐C₅H₅)(CO)₂M=P(R²)R³] (R² = R³ = Ph; R² = tBu, R³ = H; R² = Ph, R³ = N(SiMe₃)₂) Reaction of the freshly prepared phosphenium tungsten complex [(η⁵‐C₅H₅)(CO)₂W=PPh₂] ( 3 ) with the inversely polarized phosphaalkenes RP=C(NMe₂)₂ ( 1 ) ( a : R = tBu; b : Cy; c : Ph) led to the η²‐diphosphanyl complexes ( 9a‐c ) which were isolated by column chromatography as yellow crystals in 24‐30 % yield. Similarly, phosphenium complexes [(η⁵‐C₅H₅)(CO)₂M=P(H)tBu] (M = W ( 6 ); Mo ( 8 )) were converted into (M = W ( 11 ); Mo ( 12 )) by the formal abstraction of the phosphanediyl [PtBu] from 1a . Treatment of [(η⁵‐C₅H₅)(CO)₂W=P(Ph)N(SiMe₃)₂] ( 4 ) with HP=C(NMe₂)₂ ( 1d ) gave rise to the formation of yellow crystalline ( 10 ). The products were characterized by elemental analyses and spectra (IR, ¹H, ¹³C‐, ³¹P‐NMR, MS). The molecular structure of compound 10 was elucidated by an X‐ray diffraction analysis.