R-C-N Branch

Branched-chain amino sugars are also covered in Chapter 8. 

In related work, Brimacombe s group have described two separate approaches to the synthesis of the amino-precursor of (20) starting from methyl 3-acetamido-2,3,6-trideoxy-3-C-methyl-Q -L-glucopyranoside, and have also synthesized the corresponding D-enantiomer of the precursor.  

The use of 2-C-cyano-D-galactal (24) and its 3,4-0-isopropylidene derivative (25) for the synthesis of 2-C-branched chain sugars is hampered by the lack of reactivity of these glycals towards electrophilic reagents. However, addition of 

Photolysis of 3-0-acetyl-3-C-methyl-l,2 5,6-0-isopropylidene-o -D-allo-furanose yielded the corresponding 3-deoxy-3-C-methyl-D-allose derivative (see 

A variety of other unsaturated sugars have been converted into cyclopropane derivatives by addition of dihalocarbene generated in the usual way, or by the Simmons-Smith reaction. 

Reagents i, NaNa-HNs-DMF ii, Hj-Pd iii, HOAc iv, NaIO v, NaBHa vi, BzCl-py vii,CFaCOaH viii, Ac O-py 

Yoshimura, M. Matsxizawa, and M. Funabashi, Bull. Chem. Soc. Japan, 1978, 51, 2064. 

Treatment of the 3-C-substituted methylene branched-chain sugar (37) with cyanide using phase-transfer catalysis has led to the ew-di-substituted derivative (38) the 3-C-nitro-methylene analogue (39) furnished the Michael adducts (40—42).2  

Methyl 2,4-dideoxy-4-C-carboxymethyl-a-D-riZ o-hexopyranoside 2 - 3 lactone (43), required as a key intermediate for the synthesis of optically active thromboxanes, has been synthesized from D-glucose by standard transformations.  

The synthesis of branched-chain sugars by application of the Claisen rearrangement is noted in Chapter 12. 

Pillarose, a branched-chain component of the antibiotic pillaromycin A, has been shown by jy-ray crystallography i and synthesis to be a 2,3,6-trideoxy-4-C-glycolylhexose (246) and not a 2,3,6-trideoxy-2-C-glycolyIhexos-4-uIose as originally proposed (see Chapter 15). 

The selective catalytic oxidation of several 2-ulose derivatives has been studied e.g. the 2,7-anhydroheptulose (265) was selectively oxidized at the axial hydroxy-group to give the corresponding 5-ulose, which rapidly isomerized to the 2,7-anhydrohept-2,4-diulose (266). 2,3-0-Isopropylidene-j8-D-fructopyranose and 2,7-anhydro-4,5-0-isopropylidene-j8-D-a//o-hept-2-ulose were selectively oxidized at HO-4 and HO-3, respectively, whereas the furanose derivative (267) furnished the aldulosonic acid derivative (268). The reduction of these diuloses was also investigated. 

Factors governing the reduction of a number of 2- and 3-uloses derived from methyl 4,6-O-benzylidene-a- and -)3-D-glucopyranosides with sodium borohydride 

Reduction of the a-keto-oxiran (269) with sodium borohydride yielded methyl 2,3-anhydro-j3-L-ribo- and -a-o-lyxo-pyranosides in the ratio of 3 2. 3-Deoxy-D-cry/Ar 7-hexosulose has been shown to be less stable than normal carbohydrates and to polymerize within the range 100—200 °C. The poly- 

The photochemically induced 1,2-addition of furan to l,2 5,6-di-0-isopro-pylidene-a -D-r/6o-hexofuranos-3-ulose and related derivatives yielded 2,7-dioxabicyclo[3,2,0]hept-3-enes [e.g. (272)].  

A -Ray crystallography has established the stereochemistry at the branching point of methyl 3-acetamido-2,3,6-trideoxy-3C,40-dimethyl-P-L-arahino-hexopyrano-side (383), a derivative of evernitrose (384) (the nitro-sugar component of evernino-micins B, C, and Evernitrose (384) has also been synthesized from methyl 

Addition of mercuric azide to l,2 5,6-di-0-isopropylidene-3-C-methylene-a-D-r/6o-hexofuranose yielded, after reductive demercuration, the branched-chain azide (291), which could be transformed into the corresponding acetamido derivative (292). The conversion of (291) into the 3,6-acetylepimino derivative (293) established that it has the n-gluco configuration (see Vol. 9, p. 106). 

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Characterization of Natural Products Compounds with aui R -C-0R Branch Compounds with am R-C-N Branch Compounds with an R-C-H or R-C-R Breinch... 

Sugars Containing an R-C-OH Branch, 2 Compounds Containing an R-C-H or R -C-R Branch Sugars Containing an R-C-N Branch General... 

Branched-chain Sugars Compounds with an R-C-0 Branch Compounds with an r-C-N Branch... 

The synthesis of evemitrose glycosides is mentioned in Chapter 3. See also Scheme xeceding section, for the preparation of a compound with an R-C-N branch. 

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