Talose Fischer projection

Once the eight Fischer projections have been written they are named m order with the aid of the sentence All altruists gladly make gum m gallon tanks The words of the sentence stand for allose altrose glucose mannose gulose idose galactose talose... 

The aldohexoses are allose, altrose, glucose, mannose, gulose, idose, galactose, and talose. The mnemonic All altruists gladly make gum in gallon tanks is helpful in writing the conect Fischer projection for each one. 

The configuration at C-5 is opposite to that of D-(+)-glyceraldehyde. This particular carbohydrate therefore belongs to the l series. Comparing it with the Fischer projection formulas of the eight D-aldohexoses reveals it to be in the mirror image of D-(+)-talose it is l-(—)-talose... 

Three of the four hydroxyl groups at the stereogenic centers in the Fischer projection of D-talose (Figure 16.1) are on the left, yet it is called a D-sugar. Explain. 

---