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D vs L identification

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orgoquestionmcat:
Hello,

I'm studying a card, which I cannot interpret, don't know how to approach, or understand what the key takeaway is on this subject.
In what way is this figure resembling L-glyceraldehyde?

Thank you for your help.

Babcock_Hall:
Do you understand the basics of the D,L system of assigning configuration at a center of chirality?

orgoquestionmcat:
I think I'm missing some foundational rules.
According to the fischer projection, if NH2 is on the left, then it is L.
But I thought CH3 would be on the bottom, because the top carbon should be the #1 priority carbon, according to IUPAC rules.

What am I missing?

Babcock_Hall:
When assigning D and L configurations, the top carbon in the Fischer projection has the lowest IUPAC number on the top.  It is the number, not the priority, which is important.

orgoquestionmcat:
Thank you very much for your input! I fully understand now.

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