Compounds with an R-C-0 Branch

The occurrence of 6-deoxy-3-C-methyl- -D-altropyranose as a C-aryl glycoside in the antibiotic virenomycin is referred to in Chapter 19. 

Reagents i, PCC NoOAc-Mo(.sieve ii. MeMgl lit, Reslrv(OHy-MeOH iv. Tf20 v, LlEt3BH 

Reagents I, BnOCH2CHO-BF3.Et20 . ( OjjCH-PgOj- ui, OIBAL iv. fV OH- PijHOTS V, KrinO  

A new Claisen-type rearrangement for making of-substituted acrylic esters from allyl alcohols has been applied to carbohydrate 

Whereas the cyclic carbonate (23) reacts with tributylstannane to give only the expected 3-deoxy-3-C-hydroxymethyl product (24), the corresponding -hydroxyethyl derivative (25) gave both the deoxy product (26) and the 3-C-ethyl branched-chain isomer (27), the ratio depending on the concentration of the reactants. 

A convenient synthesis of D-aplose from 0-xylose using an aldol condensation of the aldehydo-sugar with formaldehyde has been described the synthesis of the requisite dl-Q-IsopropylIdene derivative is mentioned In Chapter 6. An aldol condensation of a pent-ulose with methyl propanoate giving an Intermediate branched-chain hexonlc acid derivative Is described In Chapter 24. 

A synthesis of D-evalose (6-deoxy-3-C-methyl-D-mannose) utilized an enolate methylatlon reaction for the conversion of the 4-ulose (8) to the 3-C-methyl analogue (9) LAH reduction of (9) led to the talose derivative (10), whereas NaBH reduction of the 2, 3-dl-O-acetyl analogue of (9) gave the required mannose derivative (11) 

3-ulose derivative of L-rhamnofuranose (12) selectivity for the required mannose isomer, been used to prepare the 5-ulose (13), which by Grignard reaction 

A practical procedure has been described for preparing the 3-C-formyl sugar (15) via methyl 2, 3-0-isopropylidene-D-apiofuranoside using a modified Collins oxidation (13) was required for a syn- 

Reaction of the conventional 3-ulose prepared from di-O-isopropyl-idene-D-glucofuranose with nitromethane provided both the alio- and gluco- isomers of the corresponding 3-G-nitromethyl sugars, which were then converted by standard procedures to 3-C-hydroxymethyl pentoses with D-ribo, D-xylo, and D-lyxo configurations the last of these proved to be enantiomeric with the monosaccharide isolated from Phase I Coxiella burnetii LPS, which was confirmed by a synthesis of the L-form (16) from L-arabinose using the 3-ulose (17) with lithio 1, 3-dithiane to introduce the required L-lyxo branch chain. 

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

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