Hexoses, synthesis

Balancing the Calvin Cycle Reactions To Account for Net Hexose Synthesis... 

When carbon rearrangements are balanced to account for net hexose synthesis, five of the glyceraldehyde-3-phosphate molecules are converted to dihy-droxyacetone phosphate (DHAP). Three of these DHAPs then condense with three glyceraldehyde-3-P via the aldolase reaction to yield 3 hexoses in the form... 

All the O atoms evolved as Og come from water none comes from carbon dioxide. But 12 O atoms are evolved as 6 Og, and only 6 O atoms appear as 6 HgO in the equation. Also, 6 COg have 12 O atoms, yet there are only 6 O atoms in CgHigOg. How can yon account for these discrepancies Hint Consider the partial reactions of photosynthesis ATP synthesis, NADP reduction, photolysis of water, and the overall reaction for hexose synthesis in the Calvin-Benson cycle.)... 

The essential features of the Masamune-Sharpless hexose synthesis strategy are outlined in a general way in Scheme 4. The strategy is based on the reiterative- application of a two-carbon extension cycle. One cycle comprises the following four key transformations (I) homologation of an aldehyde to an allylic alcohol (II) Sharpless asymmetric epoxidation of the allylic alcohol ... 

The second step in the hexose synthesis was the aldol condensation of 4 with another a-hetero aldehyde derivative S. By tuning the Lewis acid and the solvent, three of the four possible diastereomeric products could be selectively prepared. a-Amino and a-thio aldehydes worked well also, leading to 9 and 10 respectively. 

Four enzymes of the Calvin cycle are activated indirectly by light and are inactive in the dark, so that hexose synthesis does not compete with glycolysis—which is required to provide energy in the dark. 

Control of aerobic glycolysis and the reverse process, gluconeogenesis (hexose synthesis), in storage tissue can be mediated through the availability of ATP and the energy charge. An early step in glycolysis is the production of fructose-... 

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