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Hello! I have completely memorized how to draw all 20 amino acids in the way seen in the picture (middle, between the "ball-and-stick" and fisher projection)

By my understanding this is in the L configuration, what is the correct way of drawing them in D- configuration? Is there a simple trick? Does anyone have an image of them all drawn in D-config in the same way?

Is it basically having the COO- and NH3+ switch places. Like here:

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  • $\begingroup$ Take any two substituents at the asymmetric carbon and switch places; that would be another enantiomer. $\endgroup$ – Ivan Neretin Oct 21 '16 at 13:15
  • $\begingroup$ I can see how that would work with the fisher projections but how about in the middle drawings? Can you explain further? $\endgroup$ – Johan Oct 21 '16 at 13:27
  • $\begingroup$ Are the charges a form of hypercorrection? $\endgroup$ – DHMO Oct 21 '16 at 13:28
  • $\begingroup$ Middle drawings are no different from Fisher projections in this regard. Switch any two substituents, and you'll end up with another enantiomer. $\endgroup$ – Ivan Neretin Oct 21 '16 at 13:32
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    $\begingroup$ Swap the bold wedge and the dashed wedge. That will reverse the stereochemistry. Remember to do it for every position. This particularly important for something like isoleucine. $\endgroup$ – Zhe Oct 21 '16 at 13:47

You don't have to memorize the whole structures. Easier is to memorize the general structure including the stereochemistry, and the residues, R (except from proline). The Fisher projection is useful, but on your depiction, it's not in the usual orientation. The carbon chain should be vertical, carboxy group at the upper side, residue at the bottom. Hydrogen and amino group (pointing towards observer) horizontal.

L- and D- aminoacids and proline, Fischer projection
(non-ionized forms)

One can easily memorize that for L- amino acids, amino group is on the left, for D- amino acids the opposite, which is the case for your orientation as well (and don't forget to invert chiral residues for D- AA's, as Zhe has already noted in the discussion; it is the case for isoleucine and threonine).


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