Cyclohexylidene glyceraldehyde

Last year, a short enantioselective total synthesis of herbarumin III (42) in 11% overall yield was published the approach applied uses Keck s asymmetric allylation and Sharpless epoxidation to build the key fragment. Esterification with 5-hexenoic acid and a RCM was used to yield 42. Finally, another asymmetric synthesis of herbarumin III (42) was carried out using (R)-cyclohexylidene glyceraldehyde as the chiral template. The key steps of the synthesis were the enantioselective preparation of the... 

The use of a Maillard-type condensation to form the pyrrole fragment for the spiroketalization is rather interesting since the biosynthesis proposed by Peterson and co-workers (Scheme 10) suggests that Nature uses a similar reaction to form acortatarin A 20. In the end, they were able to access acortatarin A 20 in 14 steps, if again one does not count the steps necessary to convert D-mannitol into the cyclohexylidene glyceraldehyde 52. 

Henry reaction of the (V-acetyl-D-glucosamine derived nitrosugar 1 with 2,3-O-cyclohexylidene-D-glyceraldehyde (2) furnishes a single product 3 in 85-90% yield7. 

H. Chikashita, T. Nikaya, and K. Itoh,.Iterative and stereoselective one-carbon homologation of 1,2-O-cyclohexylidene-D-glyceraldehyde to aldose derivatives by employing 2-lithio-l,3-dithiane as a formyl anion equivalent, Nat. Product Lett. 2 183 (1993). 

The synthesis of an enantiopure p-lactam as advanced precursor of thrombin and tryptase inhibitor, has been centered on the condensation between 5-2-pyridylthio 5-(4-methoxyphenoxy)pentanoate and the AM-methoxyphenylimine derived from 0,0-cyclohexylidene D-glyceraldehyde (Scheme 23), [84]. 

In 2002, the condensation of the titanium enolate derived from 2-pyridylthio acetoxyacetate with /V-4-methoxvphenvlimine of (S)-0,0-cyclohexylidene protected glyceraldehyde has been reported to give (35.4/C4 A)-p-lactam as a single product in 65% isolated yield (Scheme 52), [137]. A reactions sequence at C-3 and C-4 led in good yield to the p-lactam inhibitor of the serine protease prostate-specific antigen. 

The nitroaldol condensation with nitromethane (Henry s reaction), followed by Nef decomposition of the resultant nitronate under strongly acidic conditions, has been used to elongate aldehydes. For instance, A-acetyl-D-mannosamine has been converted into A-acetylneuraminic acid applying this method iteratively [69]. Chikashita and coworkers [70] have reported good levels of anti diastereoselectivity better than 99% in an iterative homologation sequence using 2-lithio-l,3-dithiane [71] with 2,3-O-cyclohexylidene-D-glyceraldehyde R)-62. In the case of the BOM-protected tetrose derivative, the addition of 2-lithio-l,3-dithiane was syn selective (synlanti 82 18) (Scheme 13.30). 

O-cyclohexylidene-L-glyceraldehyde (5)-99 to 98. Double addition and higher addition reaction to yield pol)mers is alleviated by using a polymer-supported reagent [238]. 

The reaction of 2,3-0-cyclohexylidene-D-glyceraldehyde with the o-hydroxyacetyl anion equivalent (4), prepared from benzyl chloromethyl ether, 2,6-xylyl isocyanide and... 

A number of synthesis of amino-sugars from chiral non-carbohydrate starting materials have been reported. A reaction sequence used previously to synthesize 2-amino-2-deoxy-D-ribose from 2,3-0-isopropylidene-D-glyceraldehyde (V0I.I6, p.92-3) has been improved K) achieve better stereoselectivity in the initial aldol condensation used to extend the chain by two carbon atoms. The synthesis of a 6,6,6-trifluoro-L-daunosamine derivative from 2,3-0-cyclohexylidene-D-glyceraldehyde is covered in Chapter 8, and of 2,5-dideoxy-2,5-imino-pentonic acids from tartaric acid in Chapter 16. 

The cycloaddition of the 2,4-dialkoxy-l,l-difluoro-bata-l,3-diene 11 to benzyloxyacetaldehyde has afforded the unsaturated pyranoside 12 from which die racemic 2,4-dideoxy-4,4-difluotopyranosides 13 were obtained. The synthesis of 2-deoxy-2,2-difluoro-D-ribono-l,4-lactDne has been achieved by application of the Refomiatsl reaction of an ethyl difluoroacetate derivative with 2,3-0-cyclohexylidene-D-glyceraldehyde. A study of the formation of 6-deoxy-6-fluoTohexonolactones from 5,6-anhydro-hexonolactones and of 2-deoxy-2-fluoropentone-l,4-l tones from 2,3-anhydro-pentono-l,4-lactones has been reported, and the synthesis of some 3-amino-2,3-dideoxy-2-fluoro-D-xylose derivatives has been reported. ... 

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